Background/Objective: Reperfusion injury is a serious consequence of blood flow reestablishment after myocardial infarction (MI) mediated by reactive oxygen species and neutrophilic cellular damage. Following MI, the left ventricle (LV) undergoes remodeling characterized by progressive wall thinning and cavity dilatation. Heme-Oxygenase-1 (HO-1) dependent decrease in oxidative stress may attenuate injury in part by inhibiting transcription factor NFκB-mediated inflammation. Hypothesis: I hypothesized that upregulation of HO-1 by hemin administration confers acute and chronic cardioprotection against I/R injury in rats and attenuates LV remodeling post-MI. I proposed the HO-1-dependent decrease in oxidative stress attenuates post-ischemic myocardial injury in part by inhibiting NFκB-mediated inflammation. Methods: Six week old male Wistar rats were randomly assigned to sham, vehicle, or hemin-treated groups. Vehicle and hemin were administered intraperitoneally once daily for 3 consecutive days prior to left anterior descending (LAD) coronary artery occlusion. Administration resumed 48 hours post-operatively and continued once every 3 days. Infarct size was determined by H&E histological analysis and fibrosis was quantified by Masson’s Trichrome staining. Transthoracic echocardiography was used to assess LV parameters and wall motion. Results: Hemin increased HO-1 expression, decreased infarct size and fibrosis, and attenuated LV remodeling in the short-term (4 days post-infarction). The decrease in infarct size and area of fibrosis in the hemin group was accompanied by a decrease in NFκB activity. No significant difference in infarct size and area of fibrosis between hemin and vehicle-treated groups was observed at 3 months. LV diameter and cardiac function did not differ significantly between the two groups at 3 months despite an attenuation of anterior wall thinning in the hemin group. Conclusion: HO-1 upregulation by hemin administration conferred acute cardioprotection and attenuated LV remodeling, possibly by inhibiting NFκB-mediated inflammation. However, chronic treatment with hemin did not prevent long-term post-infarction LV remodeling. It is possible that cardioprotection afforded by HO-1 upregulation is strong enough to curtail inflammation post-reperfusion and prevent LV remodeling acutely, but is not robust enough to protect the myocardium to the same degree in the long-term. Future research should focus on optimal HO-1 upregulation to attenuate long-term LV remodeling due to reperfusion injury. / Thesis (Master, Physiology) -- Queen's University, 2007-09-25 19:01:33.87

Cardiovascular disease is one of the main causes of mortality and one of the significant burdens to society. Major cardiovascular diseases such as acute myocardial infarction (heart attack), heart failure and cardiac arrhythmia often result in the development of ischemia/reperfusion (I/R) injury. Untreated I/R injury is known to cause cardiac contractile dysfunction. It is established that matrix metalloproteinase-2 (MMP-2) is activated and degrades contractile proteins during I/R, and many other factors including metabolic enzymes, kinases and structural proteins are affected by I/R. However, the molecular mechanisms responsible for these changes are unclear. Since MMP-2 is known to its broad spectrum of action, I hypothesize that, in addition to contractile proteins, proteins related to regulation of energy metabolism are MMP-2 targets during I/R, and protein kinase such as myosin light chain kinase (MLCK) is also involved in this process. The use of proteomics in studying heart injury triggered by I/R will reveal new potential targets for pharmacological protection of heart from I/R induced contractile dysfunction. In addition, selective inhibition of MMP-2 using MMP-2 siRNA protects the heart from I/R injury. In this study, we investigated the protein modulation during I/R using proteomic approach. In order to study the effect of protein kinases (MLCK) and MMP-2, their selective inhibitors were used to inhibit those factors and evaluate the changes in energy metabolic proteins during I/R. Proteomic analysis revealed that six proteins are involved in energy metabolism: ATP synthase β subunit, cytochrome b-c1 complex subunit 1, 24-kDa mitochondrial NADH dehydrogenase, NADH dehydrogenase [ubiquinone] iron-sulfur protein 8, cytochrome c oxidase subunit, and succinyl-CoA ligase subunit, resulting in decreased levels in I/R hearts. The data suggests that energy metabolic proteins, especially the metabolic enzymes involved in the electron transport chain in the mitochondria may contribute to I/R injury. In addition, our data provides evidence that the right and left ventricles of the heart respond differently to I/R injury, in terms of the regulation of contractile proteins and energy metabolic enzymes. Studies using MLCK inhibitor, ML-7, and MMP-2 inhibitor, MMP-2 siRNA to investigate the effect of myosin light chain kinase (MLCK) and MMP-2 in energy metabolic proteins have shown that succinyl-CoA ligase and ATP synthase are affected by MLCK and MMP-2 respectively. These results demonstrate that the effect of inhibition of the MLCK and MMP-2 involves optimization of energy metabolism in I/R injury, likely resulting in increased energy production. Hence, the observed proteins increase in cardiac recovery after I/R. Also, inhibition of MLCK and MMP-2 by ML-7 and MMP-2 respectively shows cardio protective effect during I/R. In summary, this study provides a novel pathogenesis in the development of I/R-induced cardiac contractile dysfunction. Moreover, we suggest a new therapeutic approach whereby using MMP-2 siRNA can be a promising gene therapy in the development of new preventive or treatment strategies against I/R injury.

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Reperfusion injury may mediate renal dysfunction following ischaemia. A murine model was developed to investigate the role of the tissue factor-thrombin-protease activated receptor pathway in renal ischaemia reperfusion injury (IRI). In this model, mice received 25 minutes of ischaemia and subsequent periods of reperfusion. C57BL6, protease activated receptor-1 (PAR-1) knockout mice, and tissue factor (TF) deficient mice were used. Following 24 hours IRI, PAR-1 deficiency resulted in protection against severe renal failure compared to the C57BL6 mice (creatinine, 118.2 ?? 6.3 vs 203 ?? 12 ??mol/l, p&lt0.001). This was confirmed by lesser tubular injury. By 48 hours IRI, this resulted in a survival benefit (survival, 87.5% vs 0%, p&lt0.001). Treatment of C57BL6 mice with hirudin, a specific thrombin inhibitor, offered renoprotection at 24 hours IRI (creatinine, 107 ?? 10 ??mol/l, p&lt0.001), leading to a 60% survival rate at 48 hours IRI (p&lt0.001). TF deficient mice expressing less than 1% of C57BL6 mouse TF were also protected (creatinine, 113.6 ?? 7 ??mol/l, p&lt0.001), with a survival benefit of 75% (p&lt0.001). The PAR-1 knockout, hirudin treated C57BL6 and TF deficient mice had reduced myeloperoxidase activity and tissue neutrophil counts compared to the C57BL6 mice, along with reduced KC and MIP-2 chemokine mRNA and protein expression. Hirudin treatment of PAR-1 knockout mice had no additional benefit over PAR-1 absence alone, suggesting no further contribution by activation of other protease activated receptors (creatinine at 24 hours IRI, 106.5 ?? 10.5 ??mol/l, p&gt0.05). Furthermore, immunofluoresence staining for fibrin(ogen) showed no difference between C57BL6 and PAR-1 knockout mice, suggesting no major contribution by fibrin in this model. Renal IRI resulted in increased levels of TF mRNA expression in the C57BL6, PAR-1 knockout, and hirudin treated C57BL6 mice compared to normal controls, suggesting that TF mRNA expression was upregulated in this model. This resulted in increased TF functional activity in the C57BL6 and PAR-1 knockout mice, but TF activity was negligible in hirudin treated C57BL6 and TF deficient mice. The data therefore suggests that the TF-thrombin cascade contributes to renal IRI by signalling via PAR-1 that then regulates chemokine gene expression and subsequent neutrophil recruitment.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Diss. (sammanfattning) Göteborg : Göteborgs universitet , 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Thesis (M.D.)--University of Adelaide, Dept. of Surgery, 2002. / Includes bibliographical references (leaves 292-352).

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2009. / Härtill 4 uppsatser.