archives@tulane.edu / Experimental stroke in endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) knockout mice showed diverse effects on brain injury. nNOS and eNOS have been shown to uncouple in pathological conditions to produce superoxide. Oxidative stress is believed to be the underlying cause of several cardiovascular diseases including ischemic stroke. However, the role of eNOS and nNOS uncoupling in ischemic stroke is not well studied. Our objective of the study was to determine the effect of eNOS and nNOS inhibition on reactive oxygen species (ROS), NO, viability and mitochondrial bioenergetics in rat brain microvascular endothelial cells (BMECs) and rat cortical neurons following oxygen-glucose deprivation-reoxygenation (OGD/R). We found that non-specific inhibition of NOS in endothelial cells reduced ROS levels in BMECs but increased ROS levels in neurons under normoxia. This suggests that a pool of uncoupled NOS exists in the BMECs whereas the dominant functional NOS in neurons produces NO. We observed increased levels of ROS following OGD/R that is sensitive to NOS inhibition in both BMECs and neurons indicating eNOS and nNOS uncoupling during OGD/R. Furthermore, NOS inhibition reduced mitochondrial respiration while it improved cell survival rate in both BMECs and neurons following OGD/R. Thus, it is possible that decreased mitochondrial respiration in the immediate aftermath (4 hours) of OGD/R could be protective against reoxygenation injury. Moreover, we identified the expression of nNOS in BMECs from rat, human, and mouse. We observed that the nNOS in the BMECs constitutively produces superoxide under physiological conditions instead of NO. In contrast, nNOS in the neurons produces NO and doesn’t contribute to ROS. We also confirmed the nNOS expression and its function in freshly isolated rat brain microvessels. In addition, we developed a novel method to measure mitochondrial respiration in freshly isolated mouse brain microvessels using Seahorse XFe24 Analyzer. We validated the method by demonstrating impaired mitochondrial respiration in cerebral microvessels isolated from old mice compared to young mice. In summary, the present doctoral research investigated the distinct role of NOS isoforms in BMECs and Neurons leading to the identification of novel functional variant of nNOS in BMECs and brain microvessels. / 1 / RAMARAO SVNL

Current therapeutic options for ischemic stroke are limited to tissue plasminogen activator and mechanical clot removal therapies. Diazoxide (DZ) is a mitochondrial ATP-sensitive potassium channel opener and is protective in models of brain ischemia, but the signaling pathways involved are unknown. The mammalian target of rapamycin (mTOR) is a master regulator of protein synthesis and is involved in protection against cerebral ischemia. The neuronal nitric oxide synthase (nNOS) pathway has also been shown to provide protection from ischemic insults. Additionally, mitochondrial respiratory status has not been investigated. I examined the role of the mTOR pathway, the nNOS pathway, and mitochondrial respiration in delayed DZ-induced preconditioning of neurons. I cultured rat primary cortical neurons and simulated ischemic stroke using oxygen-glucose deprivation (OGD) for 3 h followed by re-oxygenation. Viability, mitochondrial membrane potential, reactive oxygen species (ROS) measurements, and western blots were performed. The mTOR pathway was inhibited by rapamycin, Torin-1, and S6K targeted silencing RNA. The NOS pathway was inhibited by L-NAME. NO-donors SNP and DEANONOate (DEANO) were applied to rescue the effects of L-NAME. Mitochondrial oxygen consumption rate (OCR) was measured in intact neurons by serial injections of oligomycin, FCCP, and antimycin/rotenone. OGD decreased viability by 50 percent, depolarized mitochondria, and reduced mitochondrial respiration whereas DZ improved viability to 75 percent and suppressed reactive oxygen species production, but did not restore mitochondrial membrane potential after OGD. Diazoxide also increased phosphorylation of protein kinase B, mTOR, and S6K. Rapamycin, Torin-1, and S6K targeted siRNA abolished the protective effects of DZ. Co-application of L-NAME with DZ prevented preconditioning whereas adding SNP or DEANO along with L-NAME and DZ restored protection. Diazoxide increased phosphorylated nNOS. Interestingly, co-application of LNAME with DZ blocked the phosphorylation of nNOS as well as S6K. The ratio of phosphorylated/total Akt and mTOR were not significantly altered with L-NAME co-application. Diazoxide altered OCR 24 and 48 h after the ischemic period. Diazoxide had no acute effect on OCR but increased ECAR significantly. Activation of the mTOR and nNOS pathways is critical for DZ preconditioning in neurons. Furthermore, OCR is modified by the DZ-induced preconditioning of neurons. / acase@tulane.edu

Ischemic stroke is characterized by a disruption of blood supply to a part of the brain tissue, which leads to a focal ischemic infarct. The expression and activity of MMP-9 is increased in ischemic stroke and is considered to be one of the main factors responsible for damages to the cerebral vasculature, resulting in compromised blood-brain barrier (BBB) integrity. However, the regulatory mechanisms of MMP-9 expression and activity are not well established in ischemic stroke. Since hypoxia/ischemia and reperfusion generates reactive oxygen species (ROS), I hypothesize that ROS is one of factors involved in up-regulation of MMP-9 expression in brain cells and ROS-mediated effect may occur via MAPK signaling pathway. My study has provided the evidence that ROS is responsible for an increase in MMP-9 expression in astrocytes mediated via MAPK-AP1 signaling pathway. Preliminary studies with an in vitro model of the BBB suggest that inhibition of MMP-9 is a critical component of reducing ROS-induced BBB permeability.

The disruption of the blood-brain barrier (BBB) occurs after ischemic and hemorrhagic stroke and contributes to secondary brain damage. Matrix metalloproteinase-9 (MMP9) has been identified to be the main mediator of post-stroke BBB disruption. It is unknown whether deposition of heme/iron in the brain following stroke would affect MMP9 expression. In this study, I have demonstrated that heme/iron up-regulated MMP9 expression in rat astrocytes and that this upregulation was most likely due to reactive oxygen species (ROS) generated by heme/iron deposition on cells. ROS can activate AP-1 and NFκB signaling pathways which were responsible for increased MMP9 expression. Inhibiting AP-1 and NFκB decreased MMP9 expression. Heme/iron deposition also activated Nrf-2 and increased the expression of neuroprotective heme oxygenase-1. My study suggests that heme and iron deposition generates ROS and increases MMP9 expression through AP-1 and NFκB signaling pathways and that targeting these pathways or clearance of heme and iron may modulate MMP9 expression for reduced damage.

Ischemic stroke is characterized by a disruption of blood supply to a part of the brain tissue, which leads to a focal ischemic infarct. The expression and activity of MMP-9 is increased in ischemic stroke and is considered to be one of the main factors responsible for damages to the cerebral vasculature, resulting in compromised blood-brain barrier (BBB) integrity. However, the regulatory mechanisms of MMP-9 expression and activity are not well established in ischemic stroke. Since hypoxia/ischemia and reperfusion generates reactive oxygen species (ROS), I hypothesize that ROS is one of factors involved in up-regulation of MMP-9 expression in brain cells and ROS-mediated effect may occur via MAPK signaling pathway. My study has provided the evidence that ROS is responsible for an increase in MMP-9 expression in astrocytes mediated via MAPK-AP1 signaling pathway. Preliminary studies with an in vitro model of the BBB suggest that inhibition of MMP-9 is a critical component of reducing ROS-induced BBB permeability.

The latest evidence indicates that 50,000 Canadians will experience a stroke in 2013. The hospital care, rehabilitation, and long term care associated with a stroke places a significant burden on our health care system. Lost productivity and premature death have an immeasurable impact on communities in our province as well as the rest of the country. Small, less populated regions such as Saskatchewan may be underrepresented in national data utilized in the development of national prevention and treatment strategies across the country. The absence of local research has necessitated the use of national information to guide prevention, treatment education and programming in Saskatchewan. The goals of this study was to provide a descriptive profile of stroke and transient ischemic attack cases admitted to Royal University Hospital over the period of April 1, 2009 to March 31st, 2010 and to assess the acute management of these cases as defined in the Canadian Best Practice Recommendations for Stroke Care (Strategy, 2010). A randomized sample of 200 cases 55 years and older was selected for a retrospective descriptive study involving review of adult stroke case records. Personal demographics and healthcare performance through the use of measures provided in The Canadian Best Practice Recommendations for Stroke Care (Canadian Stroke Network (CSN) and Heart and Stroke Foundation of Canada (HSFC), 2010) were evaluated. The results indicated many similarities to available national information on type of stroke, risk factors, gender, and age. Hospital adherence to national guidelines comparing selected indicators was exceeded in some areas, and met in most. The remaining indicators provide an opportunity for improvement and possibly more research. This regional information supplements the available Canadian information and could be used to guide planning and care strategically targeting Saskatchewan residents and increasing their potential for success.

The contribution of single complement system (CS) activation pathways to cerebral IR injury has not yet been adequately studied after ischemic stroke and reperfusion. It remains unclear whether a specific activation pathway (alternative, classical or lectin), single complement factors within the CS, or anaphylatoxins are responsible for increased cerebral IR injury after ischemic stroke and reperfusion. Also poorly understood is the relationship between these elements (activation pathways, CS factors and anaphylatoxins) and neutrophil mediated cerebral IR injury. The objective of this dissertation was to test the hypothesis that mannose binding lectin (MBL) deficiency during cerebral ischemia and reperfusion will result in a significant reduction of systemic neutrophil activation and cerebral injury after ischemic stroke and reperfusion via decreased CS activation and subsequent decreased anaphylatoxin production. Using the intraluminal filament method, mice with targeted mutations to MBL A/C genes (MBL-/- ) or the C57Bl/6 strain (MBL +/+ ) were subjected to 60 minutes of cerebral ischemia and either 15 minutes or 24 hours of reperfusion. After reperfusion (15 min and 24 hour) blood was removed to assess systemic neutrophil CD11b expression via flow cytometry. After 24 hours of reperfusion, the brain was removed to assess cerebral injury. CS activation after ischemic stroke and reperfusion was assessed via immunofluorescent C3 staining and RT-rtPCR methods. Our primary findings are, after ischemic stroke and reperfusion: (1) hepatic MBLA gene expression is significantly increased, (2) systemic neutrophils significantly express CD11b, (3) MBL deficiency significantly decreased cerebral infarct volume in the striatum but not in the cortex or total hemisphere, and (4) systemic neutrophil activation is independent of MBL deficiency. This study is the first to examine the contribution of MBL-initiated lectin pathway activation to cerebral IR injury after ischemic stroke and reperfusion. These findings suggest that MBL deficiency does not significantly reduce neutrophil activation or protect brain tissue after ischemic stoke and reperfusion. A complete understanding of reperfusion events after ischemic stroke is necessary for successful development of future stroke therapies to prevent cerebral IR injury. In this way, the acquisition of knowledge from the bench serves the stroke population cared for by nurses at the bedside.

Ischemic stroke is characterized by a disruption of blood supply to a part of the brain tissue, which leads to a focal ischemic infarct. The expression and activity of MMP-9 is increased in ischemic stroke and is considered to be one of the main factors responsible for damages to the cerebral vasculature, resulting in compromised blood-brain barrier (BBB) integrity. However, the regulatory mechanisms of MMP-9 expression and activity are not well established in ischemic stroke. Since hypoxia/ischemia and reperfusion generates reactive oxygen species (ROS), I hypothesize that ROS is one of factors involved in up-regulation of MMP-9 expression in brain cells and ROS-mediated effect may occur via MAPK signaling pathway. My study has provided the evidence that ROS is responsible for an increase in MMP-9 expression in astrocytes mediated via MAPK-AP1 signaling pathway. Preliminary studies with an in vitro model of the BBB suggest that inhibition of MMP-9 is a critical component of reducing ROS-induced BBB permeability.

The disruption of the blood-brain barrier (BBB) occurs after ischemic and hemorrhagic stroke and contributes to secondary brain damage. Matrix metalloproteinase-9 (MMP9) has been identified to be the main mediator of post-stroke BBB disruption. It is unknown whether deposition of heme/iron in the brain following stroke would affect MMP9 expression. In this study, I have demonstrated that heme/iron up-regulated MMP9 expression in rat astrocytes and that this upregulation was most likely due to reactive oxygen species (ROS) generated by heme/iron deposition on cells. ROS can activate AP-1 and NFκB signaling pathways which were responsible for increased MMP9 expression. Inhibiting AP-1 and NFκB decreased MMP9 expression. Heme/iron deposition also activated Nrf-2 and increased the expression of neuroprotective heme oxygenase-1. My study suggests that heme and iron deposition generates ROS and increases MMP9 expression through AP-1 and NFκB signaling pathways and that targeting these pathways or clearance of heme and iron may modulate MMP9 expression for reduced damage.

The latest evidence indicates that 50,000 Canadians will experience a stroke in 2013. The hospital care, rehabilitation, and long term care associated with a stroke places a significant burden on our health care system. Lost productivity and premature death have an immeasurable impact on communities in our province as well as the rest of the country. Small, less populated regions such as Saskatchewan may be underrepresented in national data utilized in the development of national prevention and treatment strategies across the country. The absence of local research has necessitated the use of national information to guide prevention, treatment education and programming in Saskatchewan. The goals of this study was to provide a descriptive profile of stroke and transient ischemic attack cases admitted to Royal University Hospital over the period of April 1, 2009 to March 31st, 2010 and to assess the acute management of these cases as defined in the Canadian Best Practice Recommendations for Stroke Care (Strategy, 2010). A randomized sample of 200 cases 55 years and older was selected for a retrospective descriptive study involving review of adult stroke case records. Personal demographics and healthcare performance through the use of measures provided in The Canadian Best Practice Recommendations for Stroke Care (Canadian Stroke Network (CSN) and Heart and Stroke Foundation of Canada (HSFC), 2010) were evaluated. The results indicated many similarities to available national information on type of stroke, risk factors, gender, and age. Hospital adherence to national guidelines comparing selected indicators was exceeded in some areas, and met in most. The remaining indicators provide an opportunity for improvement and possibly more research. This regional information supplements the available Canadian information and could be used to guide planning and care strategically targeting Saskatchewan residents and increasing their potential for success.