Targeting mitochondrial stability as a new therapy for stroke
Transient or permanent interruption of cerebral blood flow by occlusion of a cerebral artery gives rise to an ischaemic stroke leading to irreversible damage or dysfunction to the cells within the affected tissue along with permanent or reversible neurological deficit. Excitotoxicity, oxidative stress, inflammation and cell death are key contributory pathways underlying lesion progression. Paradoxically, restoration of blood flow (the primary therapeutic goal) can lead to exacerbation of these events through reperfusion injury. Although the brain equates to only 2% of total body weight it receives 15% of cardiac output and requires 20% of oxygen consumption. It is exceptionally sensitive to ischaemia. Mitochondria are therefore essential for normal function of the neurovascular unit as neurons are dependent on aerobic oxidative phosphorylation as a result of limited glycolytic capacity. Furthermore, through their role in calcium buffering, intracellular signalling and energy balance these organelles are central to lesion evolution. Mitochondrial “quality control” is mediated through mitochondrial biogenesis and autophagy (mitophagy) and the balance between these is perturbed after ischaemia/reperfusion such that the initiation of mitochondrial biogenesis is insufficient to counteract damage, resulting in overactivation of mitophagy. The effect of cerebral ischaemia/reperfusion on mitochondrial biogenesis/mitophagy is largely unknown. Recently, a mitochondrial-targeted S-nitrosothiol (MitoSNO) was generated to drive mitochondrial accumulation of the nitric oxide donor. Delivery of MitoSNO during reperfusion was protective in mice both ex vivo in Langendorff-perfused mouse hearts and in vivo following ischaemia/reperfusion when delivered just prior to reperfusion.
Using a robust animal model subjected to experimental stroke this studentship aims to determine the therapeutic potential of MitoSNO in cerebral ischaemia using a wide range of techniques including in vivo stroke surgery, MR imaging, molecular and biochemical analyses. MitoSNO has been shown to reduce infarct size following cardiac ischaemia/reperfusion through stabilisation of a cysteine switch in complex I of the mitochondrial respiratory chain. We have demonstrated protection of neuronal cells and cerebral endothelial cells from in vitro hypoxia/reoxygenation using MitoSNO and pilot in vivo studies show reduced infarct volume following experimental stroke. We now seek to build on and extend these studies to fully characterise the efficacy of MitoSNO following experimental stroke in an animal model displaying stroke-associated co-morbidities. Furthermore, we wish to determine the contribution of mitochondrial generated reactive oxygen species (ROS) to cerebral ischaemia and whether mitochondria biogenesis or mitophagy are altered after stroke as these important mechanistic questions have not been addressed.
Our hypothesis is that stabilisation of mitochondria in the acute phase post-experimental stroke will improve functional recovery and outcome through targeting multiple pathways affecting all cells of the neurovascular unit.
The specific objectives for the proposed PhD studentship are:
1). What are the levels of mitochondrial derived ROS production specifically following experimental stroke?
2). Do levels of mitochondria biogenesis and mitophagy alter after experimental stroke in adult SHRSP?
3). Does delivery of the mitochondrial targeted NO donor, MitoSNO, favourably influence mitochondria, oxidative stress, infarct volume and functional neurobehavioural recovery following experimental stroke? And is the proposed pathological role of complex I reactivation conserved following cerebral ischaemia/reperfusion?
Applicants must have a minimum of a 2:1 Honours degree (undergraduate) in a relevant degree.
When applying, please choose ’MVLS - PhD’ from the drop down menu and enter the project title in the free text box.
Start date is 1 October 2016
The project will be based in the Institute of Cardiovascular & Medical Sciences at the University of Glasgow (http://www.gla.ac.uk/researchinstitutes/icams/) but the work will be undertaken in collaboration with Dr Mike Murphy at the MRC Mitochondrial Biology Unit, Cambridge (http://www.mrc-mbu.cam.ac.uk/) and some time will be spent in the laboratories there.
Stipend £15,000 (year 1), £15,500 (year 2), £16,000 (year 3)