Traumatic Brain Injury (TBI) is an increasingly diagnosed constellation of injuries derived from acute mechanical trauma to the brain. With the rise of advanced neuroimaging techniques recent focus has oriented primarily towards the mild-moderate range of TBI which previously was missed diagnostically. Characteristically, these advances have shown increasing areas of micro-hemorrhage in susceptible areas of the brain and to date there are no treatment modalities targeting micro-hemorrhages or their sequelae. This dissertation explores the effects of the resulting heme processing response in the days following injury with a particular focus on inducing early heme clearance from the parenchyma using a rat central fluid percussion injury model in the mild-moderate injury range. Since heme is released ~24-48 hours post-injury and is known to be cytotoxic we observed there may be a critical window for treatment to clear heme before it is spontaneously released and to increase the buffering capacity of the tissue. We targeted heme clearance by using drugs known to increased expression of Nrf2, an upstream transcriptional regulator of the canonical heme processing protein heme oxygenase 1 (HO-1), and tracking expression of HO-1, the iron sequestration/storage proteins Lipocalin 2 (LCN2) and Ferritin (FTL), as well as the activity of matrix metalloproteinases 2 and 9 (MMP2, MMP9). We examined both tissue known to be frankly hemorrhagic (the neocortex) as well as tissue lacking any identifiable bleed (the hippocampus). We demonstrated that using the HO-1 inducers Hemin and Sulforaphane in a single dose paradigm given 1 hour post-injury heme clearance was accelerated in the neocortex with the majority of heme pigment processed by 24 hours post-injury. Further there was significant attenuation of protein expression in HO-1 and ferritin as well as the enzyme activity of MMP2 and MMP9 in both the neocortex and the hippocampus. Behavioral attenuation was also seen in both rotarod and Morris water maze tests. While we intended to target hemorrhagic processing after injury, and indeed demonstrated improved clearance of heme from post-injury hemorrhagic regions of the brain, in both tissues studied we observed remarkably similar responses to the drugs utilized in protein expression, enzyme activity, and behavioral improvement which may suggest a globally improved pathologic state or that there are unidentified pathologic micro-hemorrhages or leaky vessels which extend further into the brain parenchyma than currently identified.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-6091 |
| Date | 01 January 2017 |
| Creators | Russell, Nicholas H |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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