title: Effects of radiation on the epidermal growth factor receptor pathway in the heart.
abstract: OBJECTIVE
  Radiation-induced heart disease (RIHD) is a serious side-effect of thoracic radiotherapy. The epidermal growth factor receptor (EGFR) pathway is essential for the function and survival of cardiomyocytes. Hence, agents that target the EGFR pathway are cardiotoxic. Tocotrienols protect from radiation injury, but may also enhance the therapeutic effects of EGFR pathway inhibitors in cancer treatment. This study investigated the effects of local irradiation on the EGFR pathway in the heart and tests whether tocotrienols may modify radiation-induced changes in this pathway.
  
  
  METHODS
  Male Sprague-Dawley rats received image-guided localized heart irradiation with 21 Gy. Twenty four hours before irradiation, rats received a single dose of tocotrienol-enriched formulation or vehicle by oral gavage. At time points from 2 h to 9 months after irradiation, left ventricular expression of EGFR pathway mediators was studied.
  
  
  RESULTS
  Irradiation caused a decrease in the expression of epidermal growth factor (EGF) and neuregulin-1 (Nrg-1) mRNA from 6 h up to 10 weeks, followed by an upregulation of these ligands and the receptor erythroblastic leukemia viral oncogene homolog (ErbB)4 at 6 months. In addition, the upregulation of Nrg-1 was statistically significant up to 9 months after irradiation. A long-term upregulation of ErbB2 protein did not coincide with changes in transcription or post-translational interaction with the chaperone heat shock protein 90 (HSP90). Pretreatment with tocotrienols prevented radiation-induced changes at 2 weeks.
  
  
  CONCLUSIONS
  Local heart irradiation causes long-term changes in the EGFR pathway. Studies have to address how radiation may interact with cardiotoxic effects of EGFR inhibitors.
authors.affiliation: University of Arkansas for Medical Sciences, Department of Pharmaceutical Sciences, Division of Radiation Health, Little Rock, Arkansas 72205, USA. vmohanseenivasan@uams.edu
authors.forename: Vijayalakshmi
authors.initials: V
authors.lastname: Sridharan
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Sharma
authors.forename: Eduardo G
authors.initials: EG
authors.lastname: Moros
authors.forename: Peter M
authors.initials: PM
authors.lastname: Corry
authors.forename: Preeti
authors.initials: P
authors.lastname: Tripathi
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Lieblong
authors.forename: Chandan
authors.initials: C
authors.lastname: Guha
authors.forename: Martin
authors.initials: M
authors.lastname: Hauer-Jensen
authors.forename: Marjan
authors.initials: M
authors.lastname: Boerma
mesh_terms: D000818:Animals; D066246:ErbB Receptors / Q000378:metabolism*; D006321:Heart / Q000187:drug effects* / Q000528:radiation effects*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*; D011837:Radiation-Protective Agents / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology* / Q000528:radiation effects; D024508:Tocotrienols / Q000494:pharmacology*
chemical_list: D011837:Radiation-Protective Agents; D024508:Tocotrienols; D066246:ErbB Receptors