title: Disruption of hexokinase II-mitochondrial binding blocks ischemic preconditioning and causes rapid cardiac necrosis.
abstract: BACKGROUND
  Isoforms I and II of the glycolytic enzyme hexokinase (HKI and HKII) are known to associate with mitochondria. It is unknown whether mitochondria-bound hexokinase is mandatory for ischemic preconditioning and normal functioning of the intact, beating heart.
  
  
  OBJECTIVE
  We hypothesized that reducing mitochondrial hexokinase would abrogate ischemic preconditioning and disrupt myocardial function.
  
  
  RESULTS
  Ex vivo perfused HKII(+/-) hearts exhibited increased cell death after ischemia and reperfusion injury compared with wild-type hearts; however, ischemic preconditioning was unaffected. To investigate acute reductions in mitochondrial HKII levels, wild-type hearts were treated with a TAT control peptide or a TAT-HK peptide that contained the binding motif of HKII to mitochondria, thereby disrupting the mitochondrial HKII association. Mitochondrial hexokinase was determined by HKI and HKII immunogold labeling and electron microscopy analysis. Low-dose (200 nmol/L) TAT-HK treatment significantly decreased mitochondrial HKII levels without affecting baseline cardiac function but dramatically increased ischemia-reperfusion injury and prevented the protective effects of ischemic preconditioning. Treatment for 15 minutes with high-dose (10 μmol/L) TAT-HK resulted in acute mitochondrial depolarization, mitochondrial swelling, profound contractile impairment, and severe cardiac disintegration. The detrimental effects of TAT-HK treatment were mimicked by mitochondrial membrane depolarization after mild mitochondrial uncoupling that did not cause direct mitochondrial permeability transition opening.
  
  
  CONCLUSIONS
  Acute low-dose dissociation of HKII from mitochondria in heart prevented ischemic preconditioning, whereas high-dose HKII dissociation caused cessation of cardiac contraction and tissue disruption, likely through an acute mitochondrial membrane depolarization mechanism. The results suggest that the association of HKII with mitochondria is essential for the protective effects of ischemic preconditioning and normal cardiac function through maintenance of mitochondrial potential.
authors.affiliation: Department of Anesthesiology, Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, Amsterdam, Netherlands.
authors.forename: Kirsten M A
authors.initials: KM
authors.lastname: Smeele
authors.forename: Richard
authors.initials: R
authors.lastname: Southworth
authors.forename: Rongxue
authors.initials: R
authors.lastname: Wu
authors.forename: Chaoqin
authors.initials: C
authors.lastname: Xie
authors.forename: Rianne
authors.initials: R
authors.lastname: Nederlof
authors.forename: Alice
authors.initials: A
authors.lastname: Warley
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Nelson
authors.forename: Pepijn
authors.initials: P
authors.lastname: van Horssen
authors.forename: Jeroen P
authors.initials: JP
authors.lastname: van den Wijngaard
authors.forename: Sami
authors.initials: S
authors.lastname: Heikkinen
authors.forename: Markku
authors.initials: M
authors.lastname: Laakso
authors.forename: Anneke
authors.initials: A
authors.lastname: Koeman
authors.forename: Maria
authors.initials: M
authors.lastname: Siebes
authors.forename: Otto
authors.initials: O
authors.lastname: Eerbeek
authors.forename: Fadi G
authors.initials: FG
authors.lastname: Akar
authors.forename: Hossein
authors.initials: H
authors.lastname: Ardehali
authors.forename: Markus W
authors.initials: MW
authors.lastname: Hollmann
authors.forename: Coert J
authors.initials: CJ
authors.lastname: Zuurbier
mesh_terms: D000818:Animals; D006580:Genetic Carrier Screening; D006593:Hexokinase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology*; D009336:Necrosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D011485:Protein Binding / Q000235:genetics; D051381:Rats; D013997:Time Factors; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000502:physiology
chemical_list: D054322:tat Gene Products, Human Immunodeficiency Virus; D006593:Hexokinase