title: Lipocalin-2 induces cardiomyocyte apoptosis by increasing intracellular iron accumulation.
abstract: Our objective was to determine whether lipocalin-2 (Lcn2) regulates cardiomyocyte apoptosis, the mechanisms involved, and the functional significance. Emerging evidence suggests that Lcn2 is a proinflammatory adipokine associated with insulin resistance and obesity-related complications, such as heart failure. Here, we used both primary neonatal rat cardiomyocytes and H9c2 cells and demonstrated for the first time that Lcn2 directly induced cardiomyocyte apoptosis, an important component of cardiac remodeling leading to heart failure. This was shown by detection of DNA fragmentation using TUNEL assay, phosphatidylserine exposure using flow cytometry to detect annexin V-positive cells, caspase-3 activity using enzymatic assay and immunofluorescence, and Western blotting for the detection of cleaved caspase-3. We also observed that Lcn2 caused translocation of the proapoptotic protein Bax to mitochondria and disruption of mitochondrial membrane potential. Using transient transfection of GFP-Bax, we confirmed that Lcn2 induced co-localization of Bax with MitoTracker® dye. Importantly, we used the fluorescent probe Phen Green SK to demonstrate an increase in intracellular iron in response to Lcn2, and depleting intracellular iron using an iron chelator prevented Lcn2-induced cardiomyocyte apoptosis. Administration of recombinant Lcn2 to mice for 14 days increased cardiomyocyte apoptosis as well as an acute inflammatory response with compensatory changes in cardiac functional parameters. In conclusion, Lcn2-induced cardiomyocyte apoptosis is of physiological significance and occurs via a mechanism involving elevated intracellular iron levels and Bax translocation.
authors: Toxicity Group, and Drug Biology Group, Institut Pasteur Korea, Seongnam, Gyeonggi 463-400, South Korea.
authors: Guoxiong
authors: G
authors: Xu
authors: Jinhee
authors: J
authors: Ahn
authors: Soyoung
authors: S
authors: Chang
authors: Megumi
authors: M
authors: Eguchi
authors: Arnaud
authors: A
authors: Ogier
authors: Sungjun
authors: S
authors: Han
authors: Youngsam
authors: Y
authors: Park
authors: Chiyoung
authors: C
authors: Shim
authors: Yangsoo
authors: Y
authors: Jang
authors: Bo
authors: B
authors: Yang
authors: Aimin
authors: A
authors: Xu
authors: Yu
authors: Y
authors: Wang
authors: Gary
authors: G
authors: Sweeney
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D007501:Iron / Q000378:metabolism*; D000071068:Lipocalin-2; D054834:Lipocalins / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism* / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D000209:Acute-Phase Proteins; D017304:Annexin A5; C494827:Bax protein, mouse; C494828:Bax protein, rat; C097278:Lcn2 protein, rat; D000071068:Lipocalin-2; D054834:Lipocalins; D015513:Oncogene Proteins; D010718:Phosphatidylserines; D051028:bcl-2-Associated X Protein; C071332:Lcn2 protein, mouse; D007501:Iron; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3