Neuroprotection and Functional Alterations in Mice Over-Expressing Heat Shock Protein 70i

Kelly, Stephen (2000) Neuroprotection and Functional Alterations in Mice Over-Expressing Heat Shock Protein 70i. PhD thesis, University of Glasgow.

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Abstract

Heat Shock proteins (hsps) are induced and expressed in response to cerebral ischaemia. Pre-conditioning and cell culture studies have indicated that hsp 70i (the major inducible hsp) may be involved in reducing ischaemic neuronal damage induced by cerebral ischaemia and simulated ischaemia, respectively. Moreover, genetically modified mice and viral vectors are being increasingly employed to investigate the roles of various genes and gene products in cerebral ischaemia. The studies of this thesis were designed to address two major themes. First, the influence of hsp 70i upon ischaemic neuronal damage following global cerebral ischaemia was investigated using transgenic mice overexpressing hsp 70i and intrastriatal adenovirus (ad) hsp 70i gene transfer. Second, the functional consequences of transgene introduction into the brain were investigated, in transgenic mice over-expressing hsp 70i and in mice with intrastriatal ad enhanced green fluorescing protein (egfp, reporter gene) gene transfer. Global cerebral ischaemia in MF1 and C57bl/6 strain mice A mouse model of global cerebral ischaemia (bilateral common carotid artery occlusion, BCCAo) was established to investigate the influence of hsp 70i over-expression in the pathophysiology of cerebral ischaemia. The pathologic consequences of BCCAo in MF1 mice (the background strain of the hsp 70i transgenic mice used in this thesis) were compared with those in C57bl/6 mice (the strain most susceptible to BCCAo). Ischaemic neuronal damage in MF1 strain mice was significantly less extensive and widespread than that observed in C57bl/6 strain mice (even after extended BCCAo in MFl mice). Significantly increased posterior communicating artery (PcomA) plasticity in the circle of Willis and significantly increased mean arterial blood pressure (MABP) in MF1 strain mice during BCCAo were the most likely reasons for reduced susceptibility to BCCAo compared with C57bl/6 strain mice. Ischaemic neuronal damage in transgenic mice over-expressing hsp 70i Hsp 70i is induced in the brain by several stimuli (including cerebral ischaemia) and has been postulated to play a beneficial role in damaged cells. Following BCCAo, transgenic mice over-expressing hsp 70i displayed significantly reduced ischaemic neuronal damage in the medial caudate nucleus, lateral caudate nucleus and posterior thalamus than wild type littermate mice. PcomA plasticity and MABP during BCCAo were similar in hsp 70i transgenic and wild type littermate mice. These data indicate that transgenic hsp 70i overexpression reduces ischaemic neuronal damage induced by BCCAo. Ischaemic neuronal damage following ad hsp 70i and ad egfp gene transfer Gene transfer of therapeutic molecules by viral vectors has been shown to reduce ischaemic neuronal damage induced by both global and focal cerebral ischaemia. Intrastriatal injection of ad hsp 70i and ad egfp significantly reduced ischaemic neuronal damage in ipsilateral caudate nucleus compared with contralateral nucleus following 20-minute BCCAo, but not 10-minute BCCAo. Although ad hsp 70i and ad egfp gene transfer reduced ischaemic neuronal damage following 20-miunte BCCAo it is unlikely that they did so by the same mechanism, although this could not be concluded. Local cerebral glucose utilisation in transgenic mice over-expressing hsp 70i To investigate the impact of hsp 70i over-expression on local cerebral glucose utilisation (LCGU), 14C-2-deoxyglucose autoradiography was employed. LCGU in transgenic mice over-expressing hsp 70i was not significantly different from LCGU in wild type littermate mice in any of 35 brain regions analysed (including brain regions known to over-express hsp 70i) in the basal state. Following metabolic activation with dizocilpine (1 mg/kg) however, LCGU in transgenic mice over-expressing hsp 70i was significantly increased in three brain regions (anterior thalamus, hippocampus CA1 stratum lacunosum molecularae and hippocampus CA1 stratum oriens) and significantly decreased in two brain regions (superior olivary body and nucleus of the lateral lemniscus) compared to wild type littermate mice. These data suggest transgenic hsp 70i over-expression does not affect brain function in the basal state, but can influence brain function following metabolic activation. Local cerebral glucose utilisation following intrastriatal ad egfp gene transfer To investigate the impact of ad egfp gene transfer on LCGU, 14C-2-deoxyglucose autoradiography was employed. LCGU in areas of ad egfp transfection in ipsilateral caudate nucleus was significantly reduced compared to LCGU in the contralateral caudate nucleus at seven and 28-days post-injection. The absence of any significant differences in LCGU between hemispheres in saline injected mice at seven and 28-days post-injection, suggests that ad egfp transfer actively reduces LCGU.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Jim McCulloch
Keywords: Neurosciences, Medicine, Molecular biology
Date of Award: 2000
Depositing User: Enlighten Team
Unique ID: glathesis:2000-76147
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 16:35
Last Modified: 19 Nov 2019 16:35
URI: http://theses.gla.ac.uk/id/eprint/76147

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