UVM Theses and Dissertations
Format:
Print
Author:
Maneen, Matthew J.
Dept./Program:
Anatomy and Neurobiology
Year:
2007
Degree:
PhD
Abstract:
Cerebral ischemia and reperfusion injury (I/R) is a pathological condition affecting more than 750,000 Americans annually in the form of stroke. While I/R causes brain tissue injury, damage is not restricted to neuronal death. The reperfusion phase also contributes to vascular damage which may promote secondary brain injury through unregulated blood flow, diminished cerebral vascular resistance, blood-brain barrier disruption, and edema formation. Peroxynitrite (ONOO- ) is a reactive oxygen and nitrogen species produced from nitric oxide and superoxide following post-ischemic reperfusion that is capable of disrupting the structure and function of the cerebral vasculature including myogenic activity.
Diminished myogenic activity may disrupt autoregulation and reduce cerebral vascular resistance leading to secondary brain damage beyond the initial ischemic event. Therefore, the overall focus of this project was to investigate the underlying cellular mechanisms involved in ONOO- -induced damage to the cerebral circulation during I/R, including its influence on myogenic activity. A model of focal cerebral I/R was used to demonstrate that ONOO- was elevated in the cerebral vasculature after I/R through nitrotyrosine (NT) staining, a marker for ONOO-. In order to further explore the effect of ONOO- on the vasculature, we utilized isolated and pressurized posterior cerebral arteries from non-ischemic rats.
We hypothesized that ONOO- -induced nitrosylation of VSM actin results in depolymerization of Factin and subsequent loss of myogenic activity. NT was increased following exposure to ONOO- and was significantly colocalized with F-actin, suggesting a possible interaction of NT with F-actin. To rule out the possible involvement of potassium channels on dilation of tone, as previous studies have shown, we investigated the inhibition of specific potassium channels on dilation, loss of Factin, and NT content following ONOO- exposure.
Inhibition of potassium channels with either TEA or glibenclamide had no effect on ONOO- -induced damage, suggesting that ONOO- dilation is independent of these potassium channels in posterior cerebral arteries. Based on these findings, we hypothesize that one possible mechanism by which ONOO- diminishes myogenic tone and causes a loss of myogenic reactivity is through nitrosylation and subsequent depolymerization of VSM F-actin. This may be one area where intervention may prevent secondary brain injury following stroke.
Diminished myogenic activity may disrupt autoregulation and reduce cerebral vascular resistance leading to secondary brain damage beyond the initial ischemic event. Therefore, the overall focus of this project was to investigate the underlying cellular mechanisms involved in ONOO- -induced damage to the cerebral circulation during I/R, including its influence on myogenic activity. A model of focal cerebral I/R was used to demonstrate that ONOO- was elevated in the cerebral vasculature after I/R through nitrotyrosine (NT) staining, a marker for ONOO-. In order to further explore the effect of ONOO- on the vasculature, we utilized isolated and pressurized posterior cerebral arteries from non-ischemic rats.
We hypothesized that ONOO- -induced nitrosylation of VSM actin results in depolymerization of Factin and subsequent loss of myogenic activity. NT was increased following exposure to ONOO- and was significantly colocalized with F-actin, suggesting a possible interaction of NT with F-actin. To rule out the possible involvement of potassium channels on dilation of tone, as previous studies have shown, we investigated the inhibition of specific potassium channels on dilation, loss of Factin, and NT content following ONOO- exposure.
Inhibition of potassium channels with either TEA or glibenclamide had no effect on ONOO- -induced damage, suggesting that ONOO- dilation is independent of these potassium channels in posterior cerebral arteries. Based on these findings, we hypothesize that one possible mechanism by which ONOO- diminishes myogenic tone and causes a loss of myogenic reactivity is through nitrosylation and subsequent depolymerization of VSM F-actin. This may be one area where intervention may prevent secondary brain injury following stroke.