Hydrogen sulfide (H2S) reduces ischemia reperfusion (IR) injury by stimulating adenosine triphosphate (ATP) sensitive potassium channels (KATP) [1-5]. Demonstrating H2S stimulation is unique to KATP, as other inwardly rectifying potassium (Kir) channels demonstrate inhibition or are unaffected [6]. We recently showed that H2S inhibits Kir2 and Kir3 by decreasing channel sensitivity to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 or PIP2) [6]. Here, we test the hypothesis that H2S regulation of Kir6.2, a pore-forming subunit of the KATP channel, is also dependent on PIP2. Using whole-cell patch-clamp we show that H2S increases the activity of Kir6.2 channels expressed in HEK-293 cells. To study the mechanism, we modulated PIP2 levels by expressing a light- activated phosphatase, or by including high levels of a water-soluble PIP2 analog in the patch pipette. The results suggest that H2S augmentation of Kir6.2 channel activity is increased when PIP2 levels are elevated.

Includes bibliographical references (leaves 292-352) Determines the role of matrix metalloproteinases, MMP-2 and MMP-9 in reperfusion injury following skeletal muscle ischaemia; and, whether inhibition of MMPs by doxycycline protects against tissue damage.

Includes bibliographical references (leaves 292-352) / xvi, 352 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Determines the role of matrix metalloproteinases, MMP-2 and MMP-9 in reperfusion injury following skeletal muscle ischaemia; and, whether inhibition of MMPs by doxycycline protects against tissue damage. / Thesis (M.D.)--University of Adelaide, Dept. of Surgery, 2002

Ischemia-reperfusion (IR) injury is a severe complication in lung transplantation characterized by inflammation, alveolar damage, and hypoxemia. Alpha 1-antitrypsin (A1AT), a protease inhibitor, is currently used clinically for the treatment of A1AT deficiency emphysema. A1AT has been shown to have the potential to reduce IR injury through its anti-inflammatory and anti-apoptotic effects. We hypothesized that A1AT will ameliorate IR injury through these effects. We tested A1AT in two models of IR: a cell culture model of simulated lung transplantation and a rat in situ pulmonary ligation model. In cell culture, we found that A1AT exerts its protective effects by inhibiting cell death and inflammatory cytokine release in a dose-dependent manner. In the rat pulmonary ischemia-reperfusion model, we found that A1AT improved lung function by inhibiting apoptosis and inflammation. There is potential for future application of A1AT in the treatment of IR injury in lung transplantation.

Ischemia-reperfusion (IR) injury is a severe complication in lung transplantation characterized by inflammation, alveolar damage, and hypoxemia. Alpha 1-antitrypsin (A1AT), a protease inhibitor, is currently used clinically for the treatment of A1AT deficiency emphysema. A1AT has been shown to have the potential to reduce IR injury through its anti-inflammatory and anti-apoptotic effects. We hypothesized that A1AT will ameliorate IR injury through these effects. We tested A1AT in two models of IR: a cell culture model of simulated lung transplantation and a rat in situ pulmonary ligation model. In cell culture, we found that A1AT exerts its protective effects by inhibiting cell death and inflammatory cytokine release in a dose-dependent manner. In the rat pulmonary ischemia-reperfusion model, we found that A1AT improved lung function by inhibiting apoptosis and inflammation. There is potential for future application of A1AT in the treatment of IR injury in lung transplantation.

Thesis (M.S.)--University of Toledo, 2009. / "In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Science." Title from title page of PDF document. Bibliography: p. 39-48.

Tissue ischemia is a major cause of morbidity contributing to disease processes such as cardiovascular diseases, stroke, cancer, and traumatic injury and may lead to death. Failure to quickly reestablish flow to ischemic tissue results in tissue death. However, even timely return to normal flow has a downside in that the reintroduction of oxygen to ischemic tissue results in ischemia/reperfusion (I/R) injury that produces an oxidant stress. This pathological process requires new therapeutic strategies and agents to reduce the personal, social and economic loss. One of the most generally accepted mechanisms for the pathology of I/R injury is the production of the reactive oxygen species (ROS), suggesting antioxidants may ameliorate I/R injury. Caffeic acid phenethyl ester (CAPE), a plant derived polyphenolic compound, has been shown to protect organs from I/R induced damage in vivo, and this effect has been attributed to its antioxidant activity. To better understand the mechanism of CAPE protection, a model using menadione-induced oxidative stress in human endothelial cells to simulate I/R injury in vitro was developed. Gene expression analysis was performed with microarrays undergoing cytoprotection with CAPE. The dose-dependent cytoprotection of CAPE has been related to its induction of heme oxygenase-1 (HO-1). With the aim of improving the beneficial effect of CAPE and understanding structure activity relationship, six new catechol ring-fluorinated CAPE derivatives were synthesized and evaluated in the menadione-endothelial cell model. The data suggest good cytoprotective effects of CAPE and some analogues and indicate important structural features for cytoprotection. Further investigation of the mechanism of cytoprotection showed that cytoprotection profiles of CAPE and derivatives correlate better to their ability to induce HO-1 in human endothelial cells than free radical scavenging activity. One CAPE derivative (FCAPE) with cytoprotective effects similar to CAPE in vitro exhibited better stability in rat plasma. A validated ultra-performance liquid chromatography/tandem mass spectrometric method was developed that allowed for quantification of CAPE and FCAPE in plasma samples. Pharmacokinetic studies in male Sprague Dawley rats following intravenous bolus administration of 5, 10, and 20 mg/kg CAPE and 20 mg/kg FCAPE were performed. The results indicate that dose proportionality for CAPE does not exist in the dose range studied. Although the elimination half life was found not to be significant different between CAPE and FCAPE, significant difference was observed between the total body clearance of FCAPE and CAPE which may due to the difference in volume of distribution.

Ischemia-reperfusion (IR) injury occurs during myocardial infarction and during some cardiovascular surgeries. Animal studies support the role of endurance exercise training in preventing myocardial IR injury and coronary endothelial dysfunction. In human and animal studies, habitual exercise has been shown to attenuate endothelial dysfunction caused by aging and disease. It is unknown; however, if exercise can protect against vascular IR injury in humans and if so, whether these effects persist with advancing age. Using 20 minutes of forearm ischemia and the response of the brachial artery as a noninvasive surrogate model for the heart, the association between the mode of exercise training (endurance versus resistance) and vascular IR injury was examined in young healthy adults in the first study. Endothelial function, as measured by flow-mediated dilation (FMD) in the brachial artery, decreased significantly after forearm ischemia, suggesting that this noninvasive model of the heart produces significant and measureable vascular injury. These measures returned to baseline levels within 30 minutes following ischemia, illustrating the transient nature of this form of IR injury. The magnitude of injury and recovery from ischemia were not significantly different among young sedentary, endurance-trained, and resistance-trained subjects, suggesting that exercise training is not associated with protection from vascular IR injury in a young, healthy population. In the second study, the association between aging, endurance exercise training, and vascular IR injury was studied. Twenty minutes of forearm ischemia was associated with a transient fall in brachial FMD in young and older sedentary and endurance-trained subjects. Young subjects recovered more quickly from IR injury than older subjects. Within 30 minutes of injury, the endothelial function of the young group was back to baseline while blunted endothelial function persisted in older subjects for greater than 45 minutes after injury. There was no association between endurance exercise training and enhanced recovery from IR injury. These findings suggest that aging is associated with delayed recovery from vascular IR injury and that endurance training does not appear to modulate the vascular IR injury responses. / text

published_or_final_version / abstract / toc / Surgery / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Medicine / Master / Master of Philosophy