A postgraduate research opportunity at the University of Otago.
- Close date
- Sunday, 31 December 2017
- Academic background
- Sciences, Health Sciences
- Host campus
- On-campus or via distance?
- Dr Ailsa McGregor, Associate Professor Steve Kerr, Associate Professor Joel Tyndall
Inflammation is an important mechanism in the pathogenesis of stroke and many therapeutic approaches have targeted early inflammation in an attempt to reduce cell death. Acute inflammation also plays a key role in resolving brain injury1 and therapies that reduce the initial stage of the inflammatory response have failed to show convincing clinical benefit2. In contrast, prolonged, uncontrolled inflammation after stroke prevents tissue repair and correlates with poor outcomes in stroke patients3-6. We propose that counteracting this sub-acute phase of inflammation may be a more effective treatment approach.
Recent result from our group show that activation of anti-inflammatory pathways three days after experimental stroke reduced brain inflammation and upregulated a marker of tissue repair. Animals also demonstrated an 80% recovery in the use of their impaired paw 10 days after stroke. These results support the hypothesis that reducing chronic inflammation can promote long-term functional recovery.
In an attempt to identify targets involved in chronic inflammation we have used large-scale differential proteomics and bioinformatics to investigate changes in protein expression from 3h to 3d following focal cerebral ischemia in the mouse. One of the candidates showing early and gradual upregulation following stroke is macrophage migration inhibitory factor (MIF). MIF is a pro-inflammatory cytokine that also exhibits enzymatic activity. MIF is a key regulator of innate and acquired immunity and plays a role in both acute and chronic inflammation7. Experimental studies show that MIF is involved in the early responses to ischaemic brain injury, promotes neuronal death and aggravates neurological impairments8-10. More recently MIF has been shown to have clinical significance and high plasma levels are associated with more serious stroke symptoms11. Further, serum MIF level has been shown to correlate with infarct volume and be an independent predictor of long-term outcome 12.
While MIF neutralising antibodies and antibodies targeted to its cellular receptor CD74 have shown efficacy in mouse models of arthritis and cancer respectively7, 13, few studies have targeted MIF as a therapeutic strategy for stroke. A single study shows that the small molecule MIF inhibitor ISO-1 protects against cell death in cultured neurons exposed to oxygen-glucose deprivation 10, however this model does not recapitulate the inflammatory processes that occur following of stroke in human patients. More recently, dietary isothiocyanates have been shown to reduce MIF immunoreactivity in human plasma by 45% indicating that isothiocyanates can target MIF in complex biological systems and at physiologically achievable concentrations14. By extension, we hypothesise that isothiocyanate derivatives of these natural products15 have the potential to inhibit the upregulation of MIF that occurs following brain injury.
To determine whether novel isothiocyanate MIF inhibitors can reduce brain inflammation and improve viability in an organotypic slice culture model of stroke.
The proposed project will use an innovative in vitro organotypic slice culture model as a platform to investigate whether administration of novel small molecule isothiocyanate inhibitors of MIF in the subacute phase (24-72h) following stroke can reduce inflammation and improve brain health.
Our studies are pre-clinical animal experiments conducted in the MacGreen mouse. MacGreen transgenic mice display increased expression of a green fluorescent protein (GFP) in the damaged area of the brain after stroke and allow direct visualization of brain inflammation16.
In clinical terms, this work will provide supporting evidence to develop a pharmacological therapy which could ultimately be translated to the clinical setting. Designed to be administered in the days after stroke, this approach has significant implications for 95% of surviving stroke patients who arrive late to hospital and are not suitable for thrombolytic therapy.
An appropriate disease model is essential to establish the effectiveness of novel therapeutic strategies and to provide proof of concept which is a prerequisite to clinical testing. Oxygen-glucose deprivation (OGD) is widely used as an in vitro model for stroke, however its primary outcome measure is acute cell death and this model displays minimal inflammation. We have established an innovative in vitro model as a screening platform for compounds with anti-inflammatory effects using organotypic brain slices from MacGreen mice subjected to experimental stroke. Our model retains more anatomical integrity than dissociated neuronal cultures and allows direct assessment of brain inflammation by quantifying GFP expression.
1. Nathan C. Points of control in inflammation. Nature. 2002 Dec 19- 26;420(6917):846-52.
2. Martinez-Vila E, Irimia P. Challenges of neuroprotection and neurorestoration in ischemic stroke treatment. Cerebrovasc Dis. 2005;20 Suppl 2:148-58.
3. Manolescu BN, Berteanu M, Dumitru L, et al. Dynamics of inflammatory markers in post-acute stroke patients undergoing rehabilitation. Inflammation. 2011 Dec;34(6):551-8.
4. Candelario-Jalil E. Injury and repair mechanisms in ischemic stroke: considerations for the development of novel neurotherapeutics. Current opinion in investigational drugs. 2009 Jul;10(7):644-54.
5. Greifzu F, Schmidt S, Schmidt KF, Kreikemeier K, Witte OW, Lowel S. Global impairment and therapeutic restoration of visual plasticity mechanisms after a localized cortical stroke. Proc Natl Acad Sci U S A. 2011 Sep 13;108(37):15450-5.
6. Jablonka JA, Kossut M, Witte OW, Liguz-Lecznar M. Experience-dependent brain plasticity after stroke: effect of ibuprofen and poststroke delay. Eur J Neurosci. 2012 Sep;36(5):2632-9.
7. Savaskan NE, Fingerle-Rowson G, Buchfelder M, Eyupoglu IY. Brain miffed by macrophage migration inhibitory factor. Int J Cell Biol. 2012;2012:139573.
8. Yoshimoto T, Nishihira J, Tada M, Houkin K, Abe H. Induction of macrophage migration inhibitory factor messenger ribonucleic acid in rat forebrain by reperfusion. Neurosurgery. 1997 Sep;41(3):648-53.
9. Nishio Y, Koda M, Hashimoto M, et al. Deletion of macrophage migration inhibitory factor attenuates neuronal death and promotes functional recovery after compression-induced spinal cord injury in mice. Acta Neuropathol. 2009 Mar;117(3):321-8.
10. Inacio AR, Ruscher K, Leng L, Bucala R, Deierborg T. Macrophage migration inhibitory factor promotes cell death and aggravates neurologic deficits after experimental stroke. J Cereb Blood Flow Metab. 2011 Apr;31(4):1093-106.
11. Wang L, Zis O, Ma G, et al. Upregulation of macrophage migration inhibitory factor gene expression in stroke. Stroke. 2009 Mar;40(3):973-6.
12. Li YS, Chen W, Liu S, Zhang YY, Li XH. Serum macrophage migration inhibitory factor levels are associated with infarct volumes and long-term outcomes in patients with acute ischemic stroke. The International journal of neuroscience. 2017 Jun;127(6):539-46.
13. Li Q, He Q, Baral S, et al. MicroRNA-493 regulates angiogenesis in a rat model of ischemic stroke by targeting MIF. FEBS J. 2016 May;283(9):1720-33.
14. Brown KK, Blaikie FH, Smith RA, et al. Direct modification of the proinflammatory cytokine macrophage migration inhibitory factor by dietary isothiocyanates. J Biol Chem. 2009 Nov 20;284(47):32425-33.
15. Spencer ES, Dale EJ, Gommans AL, et al. Multiple binding modes of isothiocyanates that inhibit macrophage migration inhibitory factor. Eur J Med Chem. 2015 Mar 26;93:501-10.
16. Chen S, Bennet, L, McGregor, A. L. . MacGreen mice: a novel tool to investigate brain inflammation. Journal of Experimental Stroke and Translational Medicine. 2015;8:1-10.
ContactDr Ailsa McGregor
Tel 64 3 479 4235