Pereira 2015 Abstract MiPschool London 2015
|Ischaemia but not in vitro dissociation of heart mitochondrial-bound hexokinase II affects organelle physiology and morphology.|
Event: MiPschool London 2015
Cell injury at reperfusion after ischaemia presents a major clinical problem. Recently, we demonstrated that hexokinase II (HK2) dissociation from mitochondria during cardiac ischaemia correlates with cytochrome c (cyt c) loss, oxidative stress and subsequent reperfusion injury . Furthermore, phosphocreatine output was depressed after ischaemia suggesting broken contact sites between inner and outer mitochondrial membranes, while others have reported that contact sites breakage induces cyt c redistribution and is associated with HK2 release . However, it remains unclear whether HK2 release is the primary signal mediating ischaemia-induced mitochondrial damage. Here we assess whether HK2 depletion in vitro can mimic all the ischaemic events leading to mitochondrial damage.
Isolated hearts from Wistar rats were subject to control retrograde perfusion (pre-ischaemia), 30 min global ischaemia or to ischaemic pre-conditioning (IPC) followed by ischaemia. During isolation of mitochondria through standard methods, a portion of the sample was treated with 10 mM glucose-6-phosphate (G6P) at pH 6.3 to promote dissociation of HK2 . We demonstrate that HK2 dissociation has no effect on mitochondrial respiration (± ADP addition) regardless of the perfusion protocol. Moreover, HK2 depletion alone does not promote cyt c release. Surprisingly, complete removal of HK2 neither enhanced mPTP opening nor altered inhibition by cyclosporine A under either energised or de-energised conditions. Inner mitochondrial morphology was assessed indirectly by monitoring light scattering (LS) in the presence of ANT ligands . The amplitude of LS changes exhibited by end-ischaemia mitochondria was smaller suggesting broken contact sites. This effect was prevented by IPC but was not mimicked by in vitro HK2 depletion.
In conclusion, we were unable to replicate ischaemia-induced effects on mitochondrial function by promoting HK2 dissociation in vitro. This implies that release of mitochondrial-bound HK2 in vivo, rather than mediating mitochondrial damage directly, sensitizes mitochondria to other damaging factors.
• Keywords: HK2
• O2k-Network Lab: UK Bristol Halestrap AP
Labels: MiParea: mt-Medicine, Patients
Stress:Ischemia-reperfusion Organism: Rat Tissue;cell: Heart Preparation: Intact organ
School Biochem, Bristol Univ, UK. - email@example.com
References and Support
This work was supported by a Programme Grant from the British Heart Foundation (RG/08/001/24717)
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