title: Inhibition of Drp1 protects against senecionine-induced mitochondria-mediated apoptosis in primary hepatocytes and in mice.
abstract: Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated senecionine-induced apoptosis in primary hepatocytes. Interestingly, senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs.
authors.affiliation: The Key Laboratory of Standardization of Chinese Medicines of Ministry of Education, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 2001203, China; Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors.forename: Hong-Min
authors.initials: HM
authors.lastname: Ni
authors.affiliation: The Key Laboratory of Standardization of Chinese Medicines of Ministry of Education, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 2001203, China.
authors.forename: Aizhen
authors.initials: A
authors.lastname: Xiong
authors.affiliation: The Key Laboratory of Standardization of Chinese Medicines of Ministry of Education, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 2001203, China.
authors.forename: Zhengtao
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sesaki
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA. Electronic address: wxding@kumc.edu.
authors.forename: Wen-Xing
authors.initials: WX
authors.lastname: Ding
authors.affiliation: The Key Laboratory of Standardization of Chinese Medicines of Ministry of Education, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 2001203, China; Center for Chinese Medical Therapy and Systems Biology, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China. Electronic address: yl7@shutcm.edu.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
mesh_terms: D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D056486:Chemical and Drug Induced Liver Injury / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D034281:Dynamins / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D055786:Gene Knockout Techniques; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D011763:Pyrrolizidine Alkaloids / Q000009:adverse effects* / Q000494:pharmacology
chemical_list: D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D011763:Pyrrolizidine Alkaloids; C009237:senecionine; D000410:Alanine Transaminase; D020558:GTP Phosphohydrolases; C110768:DNM1L protein, human; C486391:Dnm1l protein, mouse; D034281:Dynamins
keywords: Apoptosis; Drp1; Liver injury; Mitochondria; Senecionine