Medicine (Northwest Academic Centre) - Research Publications
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ItemA detrimental role for nitric oxide synthase-2 in the pathology resulting from acute cerebral injury(OXFORD UNIV PRESS INC, 2004-07-01)Nitric oxide (NO) synthesized from the inducible isoform of nitric oxide synthase (NOS-2) has been suggested to play both beneficial and deleterious roles in various neuropathologies. To define the role of nitric oxide in traumatic brain injury, we subjected male mice lacking a functional NOS-2 gene (NOS-2-/-) and their wild-type littermates (NOS-2+/+) to mild or severe aseptic cryogenic cerebral injury. Expression of NOS-2 mRNA and protein was observed in NOS-2+/+ animals following injury. Lesion volume (as measured by histology and brain imaging) and neurological outcome (using motor and cognitive behavioral paradigms) were assessed at various times after injury. While magnetic resonance imaging revealed the extent of edema of the 2 genotypes to be similar, histology showed a reduced (32%) lesion volume in severely injured NOS-2-/- compared with NOS-2+/+ mice. In addition, NOS-2-/- mice showed significant improvements in both contralateral sensorimotor deficits (grid test: p = 0.011) and cognitive function (Morris water maze: p = 0.009) after severe injury compared to their wild-type littermates. This indicates that lesion volume is reduced and neurological recovery is improved after acute traumatic injury in mice lacking a functional NOS-2 gene, and strongly suggests that the post-trauma production of NO from this source contributes to neuropathology.
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ItemThe neuroprotective effect of progesterone after traumatic brain injury in male mice is independent of both the inflammatory response and growth factor expression(WILEY, 2005-03-01)Previous studies suggest that progesterone may possess neuroprotective properties after traumatic insult but, with the exception of reduced formation of cerebral oedema, limited experimental evidence has been presented to support this claim. In the present study we focused on the effect of progesterone treatment on structural and functional deficits in an experimental model of traumatic brain injury. Female mice exhibited significantly (P = 0.0445) reduced lesion volumes compared with males after aseptic cryogenic cerebral injury (ACI), suggesting that female sex steroids provide protection against this injury. In male mice, progesterone treatment after injury (three intraperitoneal doses of 8 mg/kg) reduced lesion volume (P = 0.0429) and improved performance in a spatial cognitive task (Morris water maze; P = 0.0014). However, progesterone had no demonstrable effect on the formation of oedema as measured using T2-weighted magnetic resonance imaging, nor did it affect brain water content. The pro-inflammatory cytokines TNF-alpha and IL-1beta, and growth factors BDNF and G-CSF, were all strongly transcriptionally activated after ACI. However, progesterone administration did not affect expression of these genes. This study provides strong evidence that progesterone possesses neuroprotective properties in a mouse model of traumatic brain injury, but suggests that the steroid achieves this effect through mechanism(s) independent of the inflammatory response or growth factor up-regulation.
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ItemAntagonism of the interleukin-1 receptor following traumatic brain injury in the mouse reduces the number of nitric oxide synthase-2-positive cells and improves anatomical and functional outcomes(WILEY, 2005-07-01)Interleukin (IL)-1beta plays an important role in the inflammatory response that results from traumatic brain injury and antagonism of the actions of this cytokine can affect outcome. We subjected male mice to aseptic cryogenic injury and assessed recovery through anatomical, histological and functional measures following treatment with recombinant mouse IL-1 receptor antagonist (IL-1ra). A single dose (1 microg, i.c.v.) at the time of injury reduced lesion volume 3 days later, as assessed by Nissl staining, and also the number (30%) of FluoroJade-positive degenerating neurones. Mice treated with IL-1ra performed better on the beam balance and in the grid test as compared with vehicle-treated animals. Furthermore, IL-1ra-treated animals showed fewer (40%) nitric oxide synthase-2-positive cells in and around the lesion. These data suggest that activation of the IL-1 receptor following trauma contributes to the pathology and that antagonism can reduce both anatomical and functional consequences of neuroinflammation.