title: Rac1 signalling mediates doxorubicin-induced cardiotoxicity through both reactive oxygen species-dependent and -independent pathways.
abstract: OBJECTIVE
  Doxorubicin causes damage to the heart, often leading to irreversible cardiomyopathy, which is fatal. Reactive oxygen species (ROS) or oxidative stress is involved in cardiomyocyte death, contributing to doxorubicin-induced cardiotoxicity. This study investigated the role of Rac1, an important subunit of NADPH oxidase, in doxorubicin-induced cardiotoxicity and the underlying mechanisms.
  
  
  RESULTS
  In a mouse model of acute doxorubicin-induced cardiotoxicity, cardiomyocyte-specific deletion of Rac1 inhibited NADPH oxidase activation and ROS production, prevented cardiac cell death, and improved myocardial function in Rac1 knockout mice. Therapeutic administration of the specific Rac1 inhibitor NSC23766 achieved similar cardio-protective effects in doxorubicin-stimulated mice. In rat cardiomyoblasts (H9c2 cells) and cultured neonatal mouse cardiomyocytes, Rac1 inhibition attenuated apoptosis as evidenced by decreases in caspase-3 activity and DNA fragmentation in response to doxorubicin, which correlated with a reduction in ROS production and down-regulation of p53 acetylation and histone H2AX phosphorylation. In contrast, overexpression of Rac1 enhanced apoptosis. Doxorubicin also inhibited the activity of classical histone deacetylases (HDAC), which was preserved by Rac1 inhibition and further decreased by Rac1 overexpression. Interestingly, scavenging ROS mitigated apoptosis but did not change HDAC activity and p53 acetylation stimulated by doxorubicin, suggesting both ROS-dependent and -independent pathways are involved in Rac1-mediated cardiotoxicity. Furthermore, the HDAC inhibitor trichostatin A enhanced apoptosis, p53 acetylation and H2AX phosphorylation in doxorubicin-treated cardiomyocytes.
  
  
  CONCLUSIONS
  Rac1 signalling contributes to doxorubicin-induced cardiotoxicity through both a ROS-dependent mechanism and ROS-independent HDAC/p53 signalling in cardiomyocytes. Thus, inhibition of Rac1 may be a useful therapy for doxorubicin-induced cardiotoxicity.
authors.affiliation: Department of Cardiology,  Shanghai 6th People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200233,  China.
authors.forename: Jian
authors.initials: J
authors.lastname: Ma
authors.forename: Yanpeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Dong
authors.initials: D
authors.lastname: Zheng
authors.forename: Meng
authors.initials: M
authors.lastname: Wei
authors.forename: Huaxi
authors.initials: H
authors.lastname: Xu
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
mesh_terms: D000107:Acetylation; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000633:toxicity*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006331:Heart Diseases / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019255:NADPH Oxidases / Q000378:metabolism; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D009479:Neuropeptides; C484602:Rac1 protein, mouse; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; D019255:NADPH Oxidases; C505410:Casp3 protein, rat; D053148:Caspase 3; D006655:Histone Deacetylases; C499134:Rac1 protein, rat; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein