Original Paper

Cell Death and Differentiation (2016) 23, 279–290; doi:10.1038/cdd.2015.96; published online 17 July 2015

Sirtuin 1 suppresses mitochondrial dysfunction of ischemic mouse livers in a mitofusin 2-dependent manner

T G Biel1,4, S Lee1,4, J A Flores-Toro1, J W Dean1, K L Go1, M-H Lee1, B K Law2, M E Law2, W A Dunn Jr3, I Zendejas1, K E Behrns1 and J-S Kim1,2,3

  1. 1Department of Surgery, University of Florida, Gainesville, FL, USA
  2. 2Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
  3. 3Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL, USA

Correspondence: J-S Kim, Department of Surgery, University of Florida, R4-204 ARB, 1600 SW Archer Road, Gainesville, FL 32610 USA. Tel: +1 352 392 7461; Fax: +1 352 265 1060; E-mail: Jae.Kim@surgery.ufl.edu

4These authors contributed equally to this work.

Received 29 October 2014; Revised 22 May 2015; Accepted 3 June 2015
Advance online publication 17 July 2015

Edited by N Chandel

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Abstract

Ischemia/reperfusion (I/R) injury is a major cause of morbidity and mortality after liver surgery. The role of Sirtuin 1 (SIRT1) in hepatic I/R injury remains elusive. Using human and mouse livers, we investigated the effects of I/R on hepatocellular SIRT1. SIRT1 expression was significantly decreased after I/R. Genetic overexpression or pharmacological activation of SIRT1 markedly suppressed defective autophagy, onset of the mitochondrial permeability transition, and hepatocyte death after I/R, whereas SIRT1-null hepatocytes exhibited increased sensitivity to I/R injury. Biochemical approaches revealed that SIRT1 interacts with mitofusin-2 (MFN2). Furthermore, MFN2, but not MFN1, was deacetylated by SIRT1. Moreover, SIRT1 overexpression substantially increased autophagy in wild-type cells, but not in MFN2-deficient cells. Thus, our results demonstrate that the loss of SIRT1 causes a sequential chain of defective autophagy, mitochondrial dysfunction, and hepatocyte death after I/R.

Abbreviations:

AdGFP, adenovirus encoding green fluorescence protein; AdSIRT1, adenovirus encoding sirtuin 1; Akt, AKT8 virus oncogene cellular homolog; ALLM, acetyl-Leu-Leu-Met; CHX, cycloheximide; CQ, chloroquine; GTPase, guanosine triphosphatase; IP, immunoprecipitation; I/R, ischemia/reperfusion; KRH, Krebs–Ringer–HEPES; KO, knockout; LC3, microtubule-associated protein 1 light chain 3 protein; MEF, mouse embryonic fibroblasts; MFN, mitofusin; MPT, mitochondrial permeability transition; PI, propidium iodide; Rd-123, rhodamine-123; RSV, resveratrol; shMFN2, small hairpin RNA targeting MFN2; SIRT1, sirtuin 1; TMRM, tetramethylrhodamine methylester; VDAC, voltage-dependent anion channel; WT, wild type