Upregulation of the antioxidant signalling pathway Nrf2 in acute but not chronic response to stroke caused by middle cerebral artery occlusion in mice*

1Margaux Aimable, 2Jamie McQueen, 1Emma Sigfridsson, 3Tara Spires-Jones, 2Giles Hardingham, 1Karen Horsburgh, 1Jill H. Fowler

1) Centre for Neuroregeneration, University of Edinburgh; 2) Centre for Integrative Physiology, University of Edinburgh; 3) Centre for Cognitive and Neural Systems, University of Edinburgh

Stroke (cerebral ischaemia) is a common cause of death and disability and is associated with increased risk of dementia. Two key pathophysiological mechanisms of ischaemic damage and neurodegeneration in dementia are inflammation and oxidative stress. Nrf2-signalling is a potential therapeutic target in diseases involving these mechanisms. This transcription factor drives the production of cytoprotective genes such as Heme Oxygenase-1 (hmox1), NAD(P)H dehydrogenase quinone 1 (nqo1) and Sulfiredoxin 1 (srxn1), reducing cellular oxidative damage and inflammation The aim of the current study was to characterise the acute and chronic effects of ischaemia on Nrf2 signalling and related cellular responses.

C57Bl/6 male mice underwent middle cerebral artery occlusion (MCAo) of 15 minutes (n=6-10 per group) or sham surgery and their brains harvested at acute (24hrs) and chronic (4weeks) timepoints. Indices of cellular neuroinflammation (Iba1 and GFAP) and oxidative stress (3-Nitrotyrosine) were quantified in the peri-infarct and core of the lesion using immunohistochemistry. Gene expression was analysed by qRT-PCR for hmox1, nqo1 and srxn1 following 15 mins of stroke or sham with acute (24hrs; n=5-6 per group) and chronic survival (4weeks; n=7-9 per group).

Cellular oxidative stress and inflammation was detected at 24 hours after MCAo and significantly increased with increasing duration of occlusion compared to shams. This was paralleled with a significant upregulation of the Nrf2-related genes hmox1, nqo1 and srxn1. One month following MCAo, there was a significant increase in oxidative stress and inflammation, however, hmox1 and nqo1 were not significantly altered whereas srxn1 was decreased compared to shams.

We have shown that stroke induces acute and chronic oxidative stress and inflammation in the brain, however, Nrf2-related genes are upregulated only in the acute response to ischaemia. We are currently investigating the therapeutic potential of boosting Nrf2-signalling pathway to prevent neurodegeneration caused by stroke, using transgenic and novel pharmacological approaches.

Funded by: We gratefully acknowledge funding from Alzheimer's Research UK through a senior fellowship and PhD studentship award

* entered into the PhD student poster competition