Many factors present during the perioperative period render patients susceptible in developing myocardial ischaemia reperfusion injury. Various mode of conditioning the heart against this type of injury has been discovered in animal models and involve powerful innate pathways that enhance cellular survival. These may be harnessed by applying a trigger either immediately before (preconditioning) or after (postconditioning) the lethal ischaemic injury, by physical or pharmacological means. Morphine was the first clinically used opioid shown to be cardioprotective but the intravenous dose required limited its use clinically. Remifentanil, an ultra-short acting opioid, was later also shown to be cardioprotective. A better understanding of how these opioids can protect the heart may enable the rational design of clinical regimens that best protect patients. The purpose of this thesis is to demonstrate and elucidate how these two agents provide cardiac protection. I first demonstrated the clinical efficacy of remifentanil preconditioning in reducing the release CKMB, cardiac troponin I, heart type fatty acid binding protein and ischaemia modified albumin following cardiopulmonary bypass. As opioids cannot be omitted completely from patients undergoing cardiac surgery due to ethical considerations, I then used a well-established animal model of ischaemia reperfusion injury to complete the remainder of the studies. I demonstrated that remifentanil postconditioning was also effective in reducing myocardial infarct size, an effect mediated through the activation of kappa and delta opioid receptor subtypes, and in part triggered at the level of the myocardium. I then confirmed previous findings showing the efficacy of intrathecal morphine preconditioning using clinically relevant doses. In addition, I demonstrated that all three opioid receptor subtypes were involved. This effect was comparable to that achievable by classical ischaemic or intravenous morphine preconditioning and is mediated by central but not peripheral opioid receptor activation. Intrathecal morphine reduces the degree of myocardial apoptosis, alters the phosphorylation of Akt and the expression of endothelial nitric oxide synthatase and opens the potassium ATP channels. It also involves spinal adenosine receptors, similar to spinal morphine mediated analgesia. Intrathecal morphine preconditioning can be abolished by the interruption of autonomic nervous system function and blockade of calcitonin gene related peptide (CGRP) and bradykinin receptors. Intrathecal morphine postconditioning also has an infarct sparing effect. It also involves the activation of central opioid receptors and peripheral adenosine and CGRP receptors. Finally I demonstrated a pivotal role of central opioid receptor in remote preconditioning by showing that selective blockade of these receptors abolished the protective effects of remote but not classical ischaemic preconditioning. Cumulatively, these results demonstrated the versatility of opioid mediated cardioprotection using morphine or remifentanil and the pivotal role of central opioid receptors in cardioprotection and revealed some of the mechanisms underlying these benefits. Not only does intrathecal morphine provide analgesia, it also generates signals that are transmitted through the autonomic nervous system resulting in changes in cellular function in the heart. This point to the possibility of a relationship between an organism’s intrinsic response to pain and the triggering of an innate organ protective response to ischaemia. / published_or_final_version / Anaesthesiology / Master / Doctor of Medicine

Coronary artery disease limits myocardial blood flow and results in myocardial infarction. Reperfusion therapies restore coronary flow, but may also cause myocardial ischemia reperfusion injury (MIRI). Multiple critical factors contribute to MIRI and among them, oxidative stress plays an important role. This burst of oxidative stress during reperfusion is caused by a variety of sources which collectively are called reactive oxygen species (ROS). Peroxynitrite is more cytotoxic than other ROSs, which at high concentration serves as a detrimental molecule with a variety of target. Peroxynitrite is largely produced during the early reperfusion due to the dramatically increased concentrations of superoxide (O2●-) and nitric oxide (NO). Current cardioprotective therapies against MIRI include exogenous antioxidant treatment and conditioning treatment that induced endogenous antioxidant signaling which upregulates heme oxygenase1 (HO-1), which confers its antioxidant effect in cells and tissues by degrading the latent oxidant heme and generating downstream antioxidant molecules. More importantly, peroxynitrite is closely related to HO-1 in pathogenesis of MIRI and pharmacological or genetic methods that induce over-expression of HO-1 in turn decrease the peroxynitrite generation. In this thesis we report the results of three studies designed to explore the interaction of peroxynitrite and HO-1 in cardioprotection against MIRI. In the first study we demonstrated that HO-1 plays an essential role in chronic antioxidant treatment against MIRI in 4-week diabetic rats. Chronic antioxidant treatment with two kinds of antioxidants that target different sources of ROSs was administrated in an in vivo study with streptozotocin (STZ)-induced type 1 diabetic rats. Antioxidant treatments synergistically attenuate MIRI and cardiac dysfunction in type 1 diabetic rats by enhancing HO-1 expression, and inhibition of HO-1 expression cancelled antioxidant cardioprotection. This finding was supported by in vitro experiments in a cardiomyocyte hypoxia-reoxygenation model. The second study explored the peroxynitrite/HO-1 interaction in propofol post-conditioning (PPC) in acute MIRI with both ex vivo and in vivo animal models. We showed that PPC conferred similar cardioprotection as an established intervention˗ischemic post-conditioning (I-PostC). PPC cardioprotection was achieved through down-regulating peroxynitrite formation and activation of HO-1 and its related signaling molecules. This finding indicates that anaesthetic post-conditioning treatment (such as PPC) can achieve similar cardioprotection as ischemic post-conditioning and can avoid potential mechanical injury that may be caused by I-PostC. Inhibition of peroxynitrite reduction and subsequent enhanced HO-1 expression may be the fundamental mechanism of PPC cardioprotection. Lastly, we further explored PPC cardioprotection against MIRI in diabetic rats. We found that the diabetic heart lost its sensitivity to PPC and the diminished effect of PPC in inducing HO-1 over-expression may be a key mechanism. Exogenous supplementation of adiponectin, an adipocyte-derived plasma protein with anti-diabetic and anti-inflammatory properties, restored diabetic heart sensitivity to PPC that is associated with restoration of HO-1 expression. This finding may provide a potential therapy rescuing diabetic patient challenged by myocardial infarction. The studies described in this thesis have enhanced our knowledge concerning the role of peroxynitrite in the pathogenesis of MIRI and the critical role of HO-1 in different cardioprotective therapies, in particular anaesthetic postconditioning cardioprotection. / published_or_final_version / Anaesthesiology / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

Objective Increases in the number of CD34+ stem cells and progenitor cells in blood and infarcted areas after acute myocardial infarction (AMI) are a documented phenomenon. However, no study has yet reported on the dynamic changes in specific populations of adult stem cells, such as c-kit +Lin- cells or ckit + Lin - Sca1 + (KLS cells), following AMI. This study investigated the dynamic changes in these cells in multiple systems/organs following MI in mice. Methods The C57BU6J mice received either no surgery (normal control, n=6) or surgical ligation of the left anterior descending coronary artery to create AMI (n=24). On day-1 (n=7), -3 (n=5), -6 (n=6), and -12 (n=6) after AMI, mononuclear cells were isolated from theblood, spleen, and bone marrow, and stained with Lineage-PEcy7, c-kit-PE, and Sca1-APC antibodies. The c-kit +Lin - cell and KLS cell populations in the mononuclear cells were analyzed by FACS flowcytometry. Results The pattern of changes in the c-kit + Lin - cells was very similar to that in the KLS cells in the bone marrow, circulating blood, and spleen following AMI. There was a significant increase in these cells on day-3 in the bone marrow (c-kit +Lin- cells: 1.470 ± 0.094% vs control 1.127 ± 0.019%, and KLS cells: 0.365 ± 0.012 % vs control 0.1848 ± 0.019%, p<0.05), which then slowly declined from day-6 to -12. In the blood, these cells, particularly the KLS cells, decreased slightly from day-1 to -12. On day-3, -6, and -12 the cells increased continuously and significantly in the spleen, (on day 3, c-kit +Lin-cells: 0.253 ± 0.0107 % vs control 0.1305 ± 0.014 %; it was 0.3212 ± 0.028 % on day-6). (on day-6 KLS cells: 0.1078 ± 0.076 % vs control 0.0425 ± 0.0064 % while on day 12 it was 0.1174 ± 0.035 % p<0.05). Conclusion This study provides for the first time the longest observation of the dynamic changes of specific sub-groups of adult stem cells (c-kit +Lin- cells and KLS cells) in multiple systems following AMI. The study demonstrates that AMI results in significant changes, or mobilization, of these cells in the bone marrow, spleen, and blood. Significant and continuous accumulation of the cells in the spleen occurs following AMI, despite the decreased level of the cells in the blood. The role of the spleen in stem cell mobilization after AMI is unclear and requires further investigation.

Objective Increases in the number of CD34+ stem cells and progenitor cells in blood and infarcted areas after acute myocardial infarction (AMI) are a documented phenomenon. However, no study has yet reported on the dynamic changes in specific populations of adult stem cells, such as c-kit +Lin- cells or ckit + Lin - Sca1 + (KLS cells), following AMI. This study investigated the dynamic changes in these cells in multiple systems/organs following MI in mice. Methods The C57BU6J mice received either no surgery (normal control, n=6) or surgical ligation of the left anterior descending coronary artery to create AMI (n=24). On day-1 (n=7), -3 (n=5), -6 (n=6), and -12 (n=6) after AMI, mononuclear cells were isolated from theblood, spleen, and bone marrow, and stained with Lineage-PEcy7, c-kit-PE, and Sca1-APC antibodies. The c-kit +Lin - cell and KLS cell populations in the mononuclear cells were analyzed by FACS flowcytometry. Results The pattern of changes in the c-kit + Lin - cells was very similar to that in the KLS cells in the bone marrow, circulating blood, and spleen following AMI. There was a significant increase in these cells on day-3 in the bone marrow (c-kit +Lin- cells: 1.470 ± 0.094% vs control 1.127 ± 0.019%, and KLS cells: 0.365 ± 0.012 % vs control 0.1848 ± 0.019%, p<0.05), which then slowly declined from day-6 to -12. In the blood, these cells, particularly the KLS cells, decreased slightly from day-1 to -12. On day-3, -6, and -12 the cells increased continuously and significantly in the spleen, (on day 3, c-kit +Lin-cells: 0.253 ± 0.0107 % vs control 0.1305 ± 0.014 %; it was 0.3212 ± 0.028 % on day-6). (on day-6 KLS cells: 0.1078 ± 0.076 % vs control 0.0425 ± 0.0064 % while on day 12 it was 0.1174 ± 0.035 % p<0.05). Conclusion This study provides for the first time the longest observation of the dynamic changes of specific sub-groups of adult stem cells (c-kit +Lin- cells and KLS cells) in multiple systems following AMI. The study demonstrates that AMI results in significant changes, or mobilization, of these cells in the bone marrow, spleen, and blood. Significant and continuous accumulation of the cells in the spleen occurs following AMI, despite the decreased level of the cells in the blood. The role of the spleen in stem cell mobilization after AMI is unclear and requires further investigation.

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

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.