Abstract 226: GGF2 Requires Activation Of PI3 Kinase Pathway To Mediate Cytoprotective Effects In The Mouse Atrial-derived Hl-1 Cardiomyocyte-like Cell Line
Glial growth factor (GGF2) is a Neuregulin-1 (NRG-1), which binds ErbB receptors and activates downstream cell signaling processes. NRG-1 ligands and their receptors are required for cardiac development and adult cardiac function. GGF2 has been shown to improve left ventricular function in several models of heart failure though the mechanisms by which GGF2 is efficacious are poorly understood. GGF2 is currently in clinical trials for treatment of congestive heart failure. Many studies have focused on GGF2 regulation of PI3 kinase (PI3K) as measured by formation of pAKT in vivo and in numerous cell lines, including HL-1 cells, neonatal rat ventricular myocytes (NRVMs) and human iPSC-derived cardiomyocytes. NRG-1s also activate the MAP kinase (MAPK) pathway as measured by pERK1/2 formation. To better understand GGF2 action in the stressed heart, we have developed in vitro systems to study GGF2 protection of cardiomyocytes from doxorubicin induced toxicity. After serum starvation, cells were pre-incubated with GGF2 (0.15 pM to 9.5 nM) for 1 hr followed by exposure to 1 μM doxorubicin for 18 hrs. After doxorubicin treatment MTT labeling index of cultures was used as an endpoint measurement of cell metabolic status. Doxorubicin decreases MTT labeling index by 90% while GGF2 prevented this toxicity by almost 50% compared to untreated cells, with an EC50 of 83.3±19.4 pM . This effect appears to be dependent upon AKT signaling and not MAPK as assessed using inhibitors of both pathways. Inhibition of MAPK increases pAKT formation without changing extent of GGF2 protection. Blocking ErbB4 receptor, highly expressed in cardiomyocytes, causes a decrease in pAKT formation, suggesting that this receptor is important for mediating GGF2 action in these cells. Our results demonstrate that, in HL-1 cells, GGF2 mediates cytoprotective responses which require PI3K activation. Similar studies are being pursued in doxorubicin-treated NRVMs and human iPS derived cardiomyocytes. Initial results indicate GGF2 also mediates cytoprotective effects in these cell types. Future efforts will be aimed at elucidating potential roles for PI3K-dependent GGF2 regulation of mitochondrial function, Ca2+ signaling or REDOX regulation in the observed cytoprotective actions.
Author Disclosures: M. Srinivas: None J. Cao: None R. Zilinski: None A.O. Caggiano: None D. Button: None.
- © 2014 by American Heart Association, Inc.