title: Induction of apoptosis in mouse liver by microcystin-LR: a combined transcriptomic, proteomic, and simulation strategy.
abstract: Microcystins (MCs) are a family of cyclic heptapeptide hepatotoxins produced by freshwater species of cyanobacteria that have been implicated in the development of liver cancer, necrosis, and even deadly intrahepatic bleeding. MC-LR, the most toxic MC variant, is also the most commonly encountered in a contaminated aquatic system. This study presents the first data in the toxicological research of MCs that combines the use of standard apoptotic assays with transcriptomics, proteomic technologies, and computer simulations. By using histochemistry, DNA fragmentation assays, and flow cytometry analysis, we determined that MC-LR causes rapid, dose-dependent apoptosis in mouse liver when BALB/c mice are treated with MC-LR for 24 h at doses of either 50, 60, or 70 microg/kg of body weight. We then used gene expression profiling to demonstrate differential expressions (>2-fold) of 61 apoptosis-related genes in cells treated with MC-LR. Further proteomic analysis identified a total of 383 proteins of which 35 proteins were up-regulated and 30 proteins were down-regulated more than 2.5-fold when compared with controls. Combining computer simulations with the transcriptomic and proteomic data, we found that low doses (50 microg/kg) of MC-LR lead to apoptosis primarily through the BID-BAX-BCL-2 pathway, whereas high doses of MC-LR (70 microg/kg) caused apoptosis via a reactive oxygen species pathway. These results indicated that MC-LR exposure can cause apoptosis in mouse liver and revealed two independent pathways playing a major regulatory role in MC-LR-induced apoptosis, thereby contributing to a better understanding of the hepatotoxicity and the tumor-promoting mechanisms of MCs.
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, Department of Biochemistry, Nanjing University, Nanjing 210093, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Cui
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Qian
authors.initials: Q
authors.lastname: Shi
authors.forename: Zichun
authors.initials: Z
authors.lastname: Hua
authors.forename: Jianguo
authors.initials: J
authors.lastname: Ji
authors.forename: Pingping
authors.initials: P
authors.lastname: Shen
mesh_terms: D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000502:physiology; D001427:Bacterial Toxins / Q000378:metabolism* / Q000633:toxicity; D003198:Computer Simulation; D000458:Cyanobacteria; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008387:Marine Toxins; D051379:Mice; D008807:Mice, Inbred BALB C; D052998:Microcystins; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D010456:Peptides, Cyclic / Q000378:metabolism* / Q000633:toxicity; D020543:Proteome / Q000032:analysis*; D011518:Proto-Oncogene Proteins / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2; D012313:RNA / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D051028:bcl-2-Associated X Protein / Q000502:physiology
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D001427:Bacterial Toxins; C494827:Bax protein, mouse; C494815:Bid protein, mouse; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D020543:Proteome; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; C052617:Bcl2 protein, mouse; D012313:RNA; C057862:cyanoginosin LR