Targeting the purine salvage pathway in in vitro models of cerebral ischemia
Zur Nedden, Stephanie (2011) Targeting the purine salvage pathway in in vitro models of cerebral ischemia. PhD thesis, University of Warwick.
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An interruption of the blood supply to the brain, as occurs during ischemic stroke, results in a rapid decline of ATP levels and a subsequent loss of neuronal function and viability. Under physiological conditions the brain reuses ATP degradation metabolites, such as hypoxanthine, via the purine salvage pathway, to restore its ATP pool. However, the massive degradation of ATP during ischemia results in the accumulation and loss of diffusible purine metabolites and thereby leads to a reduction in the post-ischemic ATP pool size, leaving the brain more vulnerable to secondary ischemic insults (recurrent strokes) and less able to deploy reparative mechanisms. The aim of this study was to improve the recovery of post-ischemic ATP levels by enhancing the purine salvage pathway, with substances that are already known to be tolerated in humans. Using acute hippocampal rat brain slices, I found that 1 mM Ribose (Rib) and 50 μM Adenine (Ade), two main metabolites of the purine salvage pathway, significantly increased the tissue ATP levels under basal conditions. Rib/Ade pre-treatment results in accelerated decline of synaptic transmission after onset of oxygen/glucose deprivation (OGD), due to increased adenosine release. However, this intervention does not delay the onset of anoxic depolarisation, or improve the recovery of synaptic transmission after prolonged ischemic periods. Pre-treatment of brain slices with 1 mM creatine, which increases phosphocreatine levels and thereby buffers the rapid decline of ATP levels upon energy shortage, significantly delays the onset of AD and helps to improve the recovery of synaptic transmission. By using cultured cerebellar granule cells, for more protracted studies on cell viability after OGD, I show that addition of Rib/Ade after ischemia helps to improves cell viability. Therefore my results suggest that both, delaying the decline of ATP upon onset of OGD (pre-treatment with creatine), or enhancing the post-ischemic recovery of ATP (post-treatment with Rib/Ade) are useful strategies to improve cell survival and function after in vitro ischemia.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QP Physiology|
|Library of Congress Subject Headings (LCSH):||Adenosine triphosphate, Cerebral ischemia, Ribose, Adenine, Creatine|
|Institution:||University of Warwick|
|Theses Department:||School of Life Sciences|
|Supervisor(s)/Advisor:||Frenguelli, Bruno G. ; Doney, Alexander S.|
|Sponsors:||Research into Ageing (Charitable trust)|
|Extent:||xxii, 268,  leaves : ill., charts|
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