title: Autophagy suppresses age-dependent ischemia and reperfusion injury in livers of mice.
abstract: OBJECTIVE
  As life expectancy increases, there are greater numbers of patients with liver diseases who require surgery or transplantation. Livers of older patients have significantly less reparative capacity following ischemia and reperfusion (I/R) injury, which occurs during these operations. There are no strategies to reduce the age-dependent I/R injury. We investigated the role of autophagy in the age dependence of sensitivity to I/R injury.
  
  
  METHODS
  Hepatocytes and livers from 3- and 26-month-old mice were subjected to in vitro and in vivo I/R, respectively. We analyzed changes in autophagy-related proteins (Atg). Mitochondrial dysfunction was visualized using confocal and intravital multi-photon microscopy of isolated hepatocytes and livers from anesthetized mice, respectively.
  
  
  RESULTS
  Immunoblot, autophagic flux, genetic, and imaging analyses all associated the increase in sensitivity to I/R injury with age with decreased autophagy and subsequent mitochondrial dysfunction due to calpain-mediated loss of Atg4B. Overexpression of either Atg4B or Beclin-1 recovered Atg4B, increased autophagy, blocked the onset of the mitochondrial permeability transition, and suppressed cell death after I/R in old hepatocytes. Coimmunoprecipitation analysis of hepatocytes and Atg3-knockout cells showed an interaction between Beclin-1 and Atg3, a protein required for autophagosome formation. Intravital multi-photon imaging revealed that overexpression of Beclin-1 or Atg4B attenuated autophagic defects and mitochondrial dysfunction in livers of older mice after I/R.
  
  
  CONCLUSIONS
  Loss of Atg4B in livers of old mice increases their sensitivity to I/R injury. Increasing autophagy might ameliorate liver damage and restore mitochondrial function after I/R.
authors.affiliation: Department of Surgery, Division of Biology of Aging, University of Florida, Gainesville, Florida, USA.
authors.forename: Jin-Hee
authors.initials: JH
authors.lastname: Wang
authors.forename: In-Sook
authors.initials: IS
authors.lastname: Ahn
authors.forename: Trevan D
authors.initials: TD
authors.lastname: Fischer
authors.forename: Jae-Il
authors.initials: JI
authors.lastname: Byeon
authors.forename: William A
authors.initials: WA
authors.lastname: Dunn
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Behrns
authors.forename: Christiaan
authors.initials: C
authors.lastname: Leeuwenburgh
authors.forename: Jae-Sung
authors.initials: JS
authors.lastname: Kim
mesh_terms: D000367:Age Factors; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D001343:Autophagy / Q000502:physiology*; D000071183:Autophagy-Related Proteins; D000071186:Beclin-1; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D022781:Hepatocytes / Q000473:pathology; D015151:Immunoblotting; D047468:Immunoprecipitation; D008107:Liver Diseases / Q000378:metabolism / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D036641:Microscopy, Fluorescence, Multiphoton; D015427:Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071183:Autophagy-Related Proteins; D000071186:Beclin-1; C115010:Becn1 protein, mouse; C582881:Atg4b protein, mouse; D003546:Cysteine Endopeptidases