Cardiac Endothelial Cells Regulate Reactive Oxygen Species-induced Cardiomyocyte Apoptosis through Neuregulin-1β/erbB4 Signaling

Abstract

Neuregulin (NRG)-1␤ has a prosurvival effect on cardiac myocytes via the phosphatidylinositol-3-kinase/Akt pathway, but the physiological regulators of this system in the intact heart are unknown. In this study, we tested the hypothesis that reactive oxygen species regulate NRG/erbB signaling. We used isolated adult rat ventricular myocytes (ARVMs) or cardiac microvascular endothelial cells (CMECs) in monoculture, or together in coculture. H 2 O 2 induced NRG-1␤ release from CMECs in a concentration-dependent manner, and conditioned medium from H 2 O 2 -treated CMEC activated ARVM erbB4. NRG-1␤ release occurred via proteolytic cleavage of 115-kDa transmembrane NRG-1␤ and was inhibited by the metalloproteinase inhibitor 1,10-phenanthroline. In myocyte monoculture, H 2 O 2 induced erbB4-dependent, but NRG-independent, activation of Akt. To elucidate the bioactivity of CMEC-derived NRG-1␤ on ARVMs, we examined H 2 O 2 -induced myocyte apoptosis in co-culture using an antibody to NRG-1␤. The percentages of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly higher in the anti-NRG-1␤ group than in the control group. The change in apoptosis induced by anti-NRG-1␤ in co-culture was similar in magnitude to the protection of myocytes by addition of recombinant NRG-1␤ to ARVM monocultures. Activation of NRG/erbB paracrine signaling was also seen in the intact heart subjected to oxidative stress by ischemia-reperfusion injury. Isolated perfused mouse hearts subjected to 15 min of ischemia, followed by 30 min of reperfusion, showed complete proteolytic cleavage of 115-kDa NRG-1␤, with concomitant erbB4 phosphorylation. These results demonstrate that reactive oxygen species activate NRG-1␤/erbB4 paracrine signaling in the heart and suggest that this system is involved in cardiac adaptation to oxidative stress. Neuregulin-1 (NRG)1 /erbB signaling is essential for cardiac development (1-5). Moreover, cardiotoxicity of trastuzumab (Herceptin), an erbB2-targeted antibody used in treatment of erbB2-positive cancer, suggests that this pathway also plays a role in the regulation of cardiac structure and function in the postnatal heart (6). Cardiac microvascular endothelial cells (CMECs) express NRG (7), and recombinant NRG-1␤ protects myocytes against anthracycline-and ␤-adrenergic receptor-induced cell injury and death (8 -10). This prosurvival effect of NRG-1␤ occurs through the activation of erbB2 and erbB4 receptor tyrosine kinases in myocytes with downstream signaling in the phosphatidylinositol-3-kinase/Akt pathway. The in vivo role of erbB signaling in cardioprotection is further supported by the finding that mice with a cardiac-specific erbB2 conditional knock-out survive to birth but have accelerated heart failure after injury by pressure-overload or Adriamycin (11, 12). These observations suggest that the NRG/erbB pathway acts as a stress-responsive signal between CMECs and myocytes to maintain cell survival and cardiac function.We have cloned eight isoforms of NRG-1␤ fr...

Endogenous Neuregulin Restores Radial Glia in a (Ferret) Model of Cortical Dysplasia

“…Falls, 2003). The size of released, soluble NRG1 forms found in conditioned media varies considerably depending on the experimental system being used, the domain structure, and glycosylation level and may range from 40 to 80 kDa (Holmes et al, 1992;Ethier et al, 1996;Pollock et al, 1999;Villegas et al, 2000;Wang et al, 2001;Malave et al, 2003;Stove et al, 2003;Kuramochi et al, 2004). The size of the NRG1 isoform that we found in normal cortex-conditioned medium falls within this range.…”

Neuregulin activates erbB2-dependent src/FAK signaling and cytoskeletal remodeling in isolated adult rat cardiac myocytes

“…Our present findings predict that these mice will show specific impairment in NRG-1β-dependent activation of Src/FAK signaling and FAC formation, particularly under stressed conditions. In preliminary experiments, we have found that the potent activation of NRG-1β/erbB signaling by myocardial ischemia-reperfusion injury [35] is accompanied by phosphorylation of FAK at Y861, and formation of a FAK/erbB2 complex (Kuramochi, Lim and Sawyer, unpublished observation). A morphological analysis of the erbB2 knockout mice during such a stress will help to elucidate the functional significance of the erbB2/Src/FAK pathway.…”

Diminished survival of human cytotrophoblast cells exposed to hypoxia/reoxygenation injury and associated reduction of heparin-binding epidermal growth factor-like growth factor

“…In proximal renal tubule cells, reoxygenation following hypoxia results in activation of MEK/ERK and PI3K/Akt/XIAP survival signaling pathways, which are mediated through HER1 (20). The anti-apoptotic action of neuregulin 1-β, another member of the EGF-like family, requires phosphorylation of HER-4 in rat hearts exposed to ischemiareperfusion injury (21).…”