title: Epidermal Growth Factor Receptor Silencing Blunts the Slow Force Response to Myocardial Stretch.
abstract: Myocardial stretch increases force biphasically: the Frank-Starling mechanism followed by the slow force response (SFR). Based on pharmacological strategies, we proposed that epidermal growth factor (EGF) receptor (EGFR or ErbB1) activation is crucial for SFR development. Pharmacological inhibitors could block ErbB4, a member of the ErbB family present in the adult heart. We aimed to specifically test the role of EGFR activation after stretch, with an interference RNA incorporated into a lentiviral vector (small hairpin RNA [shRNA]-EGFR).
  
  
  
  Silencing capability of p-shEGFR was assessed in EGFR-GFP transiently transfected HEK293T cells. Four weeks after lentivirus injection into the left ventricular wall of Wistar rats, shRNA-EGFR-injected hearts showed ≈60% reduction of EGFR protein expression compared with shRNA-SCR-injected hearts. ErbB2 and ErbB4 expression did not change. The SFR to stretch evaluated in isolated papillary muscles was ≈130% of initial rapid phase in the shRNA-SCR group, while it was blunted in shRNA-EGFR-expressing muscles. Angiotensin II (Ang II)-dependent Na+/H+ exchanger 1 activation was indirectly evaluated by intracellular pH measurements in bicarbonate-free medium, demonstrating an increase in shRNA-SCR-injected myocardium, an effect not observed in the silenced group. Ang II- or EGF-triggered reactive oxygen species production was significantly reduced in shRNA-EGFR-injected hearts compared with that in the shRNA-SCR group. Chronic lentivirus treatment affected neither the myocardial basal redox state (thiobarbituric acid reactive substances) nor NADPH oxidase activity or expression. Finally, Ang II or EGF triggered a redox-sensitive pathway, leading to p90RSK activation in shRNA-SCR-injected myocardium, an effect that was absent in the shRNA-EGFR group.
  
  
  
  Our results provide evidence that specific EGFR activation after myocardial stretch is a key factor in promoting the redox-sensitive kinase activation pathway, leading to SFR development.
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: María S
authors.initials: MS
authors.lastname: Brea
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Romina G
authors.initials: RG
authors.lastname: Díaz
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Daiana S
authors.initials: DS
authors.lastname: Escudero
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Claudia I
authors.initials: CI
authors.lastname: Caldiz
authors.affiliation: Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, Buenos Aires, Argentina.
authors.forename: Enrique L
authors.initials: EL
authors.lastname: Portiansky
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Patricio E
authors.initials: PE
authors.lastname: Morgan
authors.affiliation: Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina gperez@med.unlp.edu.ar.
authors.forename: Néstor G
authors.initials: NG
authors.lastname: Pérez
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D049452:Green Fluorescent Proteins; D057809:HEK293 Cells; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D034741:RNA, Small Interfering; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D066247:Receptor, ErbB-4 / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1 / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000804:Angiotensin II; D066246:ErbB Receptors; D049452:Green Fluorescent Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D018719:Erb-b2 Receptor Tyrosine Kinases; D066247:Receptor, ErbB-4; D000074082:Sodium-Hydrogen Exchanger 1; D014662:Vasoconstrictor Agents; C452850:Slc9a1 protein, rat; C512478:EGFR protein, human; C483803:Egfr protein, rat; C483804:Erbb2 protein, rat; C587691:Erbb4 protein, rat
keywords: epidermal growth factor receptor; interference RNA; myocardial stretch