Abstract: Thrombo-occlusive cerebrovascular disease resulting in stroke and permanent neuronal loss is an important cause of morbidity and mortality. Because of the unique properties of cerebral vasculature and the limited reparative capability of neuronal tissue, it has been difficult to devise effective neuroprotective therapies in cerebral ischemia. Our results demonstrate that systemic administration of human cord blood-derived CD34 + cells to immunocompromised mice subjected to stroke 48 hours earlier induces neovascularization in the ischemic zone and provides a favorable environment for neuronal regeneration. Endogenous neurogenesis, suppressed by an antiangiogenic agent, is accelerated as a result of enhanced migration of neuronal progenitor cells to the damaged area, followed by their maturation and functional recovery. Our data suggest an essential role for CD34 + cells in promoting directly or indirectly an environment conducive to neovascularization of ischemic brain so that neuronal regeneration can proceed.

Abstract: AMP-activated protein kinase (AMPK) is an important regulator of diverse cellular pathways in the setting of energetic stress. Whether AMPK plays a critical role in the metabolic and functional responses to myocardial ischemia and reperfusion remains uncertain. We examined the cardiac consequences of long-term inhibition of AMPK activity in transgenic mice expressing a kinase dead (KD) form of the enzyme. The KD mice had normal fractional shortening and no heart failure, cardiac hypertrophy, or fibrosis, although the in vivo left ventricular (LV) dP/dt was lower than that in WT hearts. During low-flow ischemia and postischemic reperfusion in vitro, KD hearts failed to augment glucose uptake and glycolysis, although glucose transporter content and insulin-stimulated glucose uptake were normal. KD hearts also failed to increase fatty acid oxidation during reperfusion. Furthermore, KD hearts demonstrated significantly impaired recovery of LV contractile function during postischemic reperfusion that was associated with a lower ATP content and increased injury compared with WT hearts. Caspase-3 activity and TUNEL-staining were increased in KD hearts after ischemia and reperfusion. Thus, AMPK is responsible for activation of glucose uptake and glycolysis during low-flow ischemia and plays an important protective role in limiting damage and apoptotic activity associated with ischemia and reperfusion in the heart.

Abstract: Current knowledge regarding the pathophysiology of cerebral ischemia and brain trauma indicates that similar mechanisms contribute to loss of cellular integrity and tissue destruction. Mechanisms of cell damage include excitotoxicity, oxidative stress, free radical production, apoptosis and inflammation. Genetic and gender factors have also been shown to be important mediators of pathomechanisms present in both injury settings. However, the fact that these injuries arise from different types of primary insults leads to diverse cellular vulnerability patterns as well as a spectrum of injury processes. Blunt head trauma produces shear forces that result in primary membrane damage to neuronal cell bodies, white matter structures and vascular beds as well as secondary injury mechanisms. Severe cerebral ischemic insults lead to metabolic stress, ionic perturbations, and a complex cascade of biochemical and molecular events ultimately causing neuronal death. Similarities in the pathogenesis of these cerebral injuries may indicate that therapeutic strategies protective following ischemia may also be beneficial after trauma. This review summarizes and contrasts injury mechanisms after ischemia and trauma and discusses neuroprotective strategies that target both types of injuries.

Abstract: Despite numerous defenses, the brain is vulnerable to oxidative stress resulting from ischemia/reperfusion. Excitotoxic stimulation of superoxide and nitric oxide production leads to formation of highly reactive products, including peroxynitrite and hydroxyl radical, which are capable of damaging lipids, proteins and DNA. Use of transgenic mutants and selective pharmacological antioxidants has greatly increased understanding of the complex interplay between substrate deprivation and ischemic outcome. Recent evidence that reactive oxygen/nitrogen species play a critical role in initiation of apoptosis, mitochondrial permeability transition and poly(ADP-ribose) polymerase activation provides additional mechanisms for oxidative damage and new targets for post-ischemic therapeutic intervention. Because oxidative stress involves multiple post-ischemic cascades leading to cell death, effective prevention/treatment of ischemic brain injury is likely to require intervention at multiple effect sites.

Abstract: Nitric oxide (NO.) is thought to protect against the damaging effects of myocardial ischemia-reperfusion injury, whereas xanthine oxidoreductase (XOR) normally causes damage through the generation of reactive oxygen species. In the heart, inorganic nitrite (NO(2)(-)) has the potential to act as an endogenous store of NO., liberated specifically during ischemia. Using a detection method that we developed, we report that under ischemic conditions both rat and human homogenized myocardium and the isolated perfused rat heart (Langendorff preparation) generate NO. from NO(2)(-) in a reaction that depends on XOR activity. Functional studies of rat hearts in the Langendorff apparatus showed that nitrite (10 and 100 microM) reduced infarct size from 47.3 +/- 2.8% (mean percent of control +/- SEM) to 17.9 +/- 4.2% and 17.4 +/- 1.0%, respectively (P < 0.001), and was associated with comparable improvements in recovery of left ventricular function. This protective effect was completely blocked by the NO. scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide (carboxy-PTIO). In summary, the generation of NO. from NO(2)(-), by XOR, protects the myocardium from ischemia-reperfusion injury. Hence, if XOR is presented with NO(2)(-) as an alternative substrate, the resultant effects of its activity may be protective, by means of its production of NO. , rather than damaging.

Abstract: Ischemia-reperfusion injury of the intestine is a significant problem in abdominal aortic aneurysm surgery, small bowel transplantation, cardiopulmonary bypass, strangulated hernias, and neonatal necrotizing enterocolitis. It can also occur as a consequence of collapse of systemic circulation, as in hypovolemic and septic shock. It is associated with a high morbidity and mortality. This article is a comprehensive review of the current status of the molecular biology and the strategies to prevent ischemia-reperfusion injury of the intestine. Various treatment modalities have successfully been applied to attenuate reperfusion injury in animal models of reperfusion injury of the intestine. Ischemic preconditioning has been found to be the most promising strategy against reperfusion injury during the last few years, appearing to increase the tolerance of the intestine to reperfusion injury. Although ischemic preconditioning has been shown to be beneficial in the human heart and the liver, prospective controlled studies in humans involving ischemic preconditioning of the intestine are lacking. Research focused on the application of novel drugs that can mimic the effects of ischemic preconditioning to manipulate the cellular events during reperfusion injury of the intestine is required.

Abstract: Background— Myocardial ischemia and reperfusion-induced tissue injury involve a robust inflammatory response, but the proximal events in reperfusion injury remain incompletely defined. Toll-like receptor 4 (TLR4) is a proximal signaling receptor in innate immune responses to lipopolysaccharide of Gram-negative pathogens. TLR4 is also expressed in the heart and vasculature, but a role for TLR4 in the myocardial response to injury separate from microbial pathogens has not been examined. This study assessed the role of TLR4 in myocardial infarction and inflammation in a murine model of ischemia-reperfusion injury. Methods and Results— Myocardial ischemia-reperfusion (MIR) was performed on 2 strains of TLR4-deficient mice (C57/BL10 ScCr and C3H/HeJ) and controls (C57/BL10 ScSn and C3H/OuJ). Mice were subjected to 1 hour of coronary ligation, followed by 24 hours of reperfusion. TLR4-deficient mice sustained significantly smaller infarctions compared with control mice given similar areas at risk. Fewer neutrop...

Abstract: Administration of nitric oxide (NO), NO donors or drugs that enhance NO release (statins, calcium antagonists, ACE-inhibitors, dexamethasone) prior to ischemia protects the myocardium against ischemia/reperfusion injury. While this exogenous administration of NO prior to ischemia can initiate a preconditioning-like phenomenon, endogenous NO-synthase (NOS)-derived NO is not involved in triggering or mediating the early phase of ischemic preconditioning's protection, but does play a pivotal role for initiating and mediating the delayed phase of ischemic preconditioning's protection. The present review now summarizes the importance of endogenous and exogenous NO when given at the time of reperfusion for vascular and myocardial function and morphological outcome following ischemia/reperfusion. Given the inconsistency of the published data, potential confounding factors that might affect experimental results on the role of NO in myocardial ischemia/reperfusion were identified, such as (1) the lack of characterization of the involved NOS isoforms in myocardial ischemia/reperfusion injury in different animal species, (2) the lack of direct measurements of myocardial NO concentration and/or NOS activity to assure sufficient NOS inhibition, (3) the lack of consideration of nonenzymatic NO production as a potential source of NO, and (4) the absence of plasma or blood components in in vitro studies influencing NO delivery and metabolism. Future research on the importance of NO in ischemia/reperfusion injury will have to focus more precisely on the identification and standardization of potential confounding experimental factors that influence synthesis, transport, and interaction of NO with various targets in blood and tissue.

Abstract: ContextRecent studies suggest that factors other than the degree of carotid stenosis are involved in ischemic stroke pathogenesis, especially modifications of plaque composition and related complications.ObjectiveTo examine the role of carotid plaque rupture and thrombosis in ischemic stroke pathogenesis in patients undergoing carotid endarterectomy, excluding those with possible cardiac embolization or with severe stenosis of the circle of Willis.Design, Setting, and PatientsA total of 269 carotid plaques selected from an Interinstitutional Carotid Tissue Bank were studied by histology after surgical endarterectomy between January 1995 and December 2002. A total of 96 plaques were from patients with ipsilateral major stroke, 91 plaques from patients with transient ischemic attack (TIA), and 82 plaques from patients without symptoms.Main Outcome MeasuresDifferences in the frequency of thrombosis, cap rupture, cap erosion, inflammatory infiltrate, and major cardiovascular risk factors between study groups.ResultsA thrombotically active carotid plaque associated with high inflammatory infiltrate was observed in 71 (74.0%) of 96 patients with ipsilateral major stroke (and in all 32 plaques from patients operated within 2 months of symptom onset) compared with 32 (35.2%) of 91 patients with TIA (P < .001) or 12 (14.6%) of 82 patients who were without symptoms (P < .001). In addition, a fresh thrombus was observed in 53.8% of patients with stroke operated 13 to 24 months after the cerebrovascular event. An acute thrombus was associated with cap rupture in 64 (90.1%) of 71 thrombosed plaques from patients with stroke and with cap erosion in the remaining 7 cases (9.9%). Ruptured plaques of patients affected by stroke were characterized by the presence of a more severe inflammatory infiltrate, constituted by monocytes, macrophages, and T lymphocyte cells compared with that observed in the TIA and asymptomatic groups (P = .001). There was no significant difference between groups in major cardiovascular risk factors.ConclusionThese results demonstrate a major role of carotid thrombosis and inflammation in ischemic stroke in patients affected by carotid atherosclerotic disease.

Abstract: Although restoration of blood flow to an ischaemic organ is essential to prevent irreversible tissue injury, reperfusion per se may result in a local and systemic inflammatory response that may augment tissue injury in excess of that produced by ischaemia alone. Cellular damage after reperfusion of previously viable ischaemic tissues is defined as ischaemia-reperfusion (I-R) injury. I-R injury is characterized by oxidant production, complement activation, leucocyte-endothelial cell adhesion, platelet-leucocyte aggregation, increased microvascular permeability and decreased endothelium-dependent relaxation. In its severest form, I-R injury can lead to multiorgan dysfunction or death. Although our understanding of the pathophysiology of I-R injury has advanced significantly in the last decade, such experimentally derived concepts have yet to be fully integrated into clinical practice. Treatment of I-R injury is also confounded by the fact that inhibition of I-R-associated inflammation might disrupt protective physiological responses or result in immunosuppression. Thus, while timely reperfusion of the ischaemic area at risk remains the cornerstone of clinical practice, therapeutic strategies such as ischaemic preconditioning, controlled reperfusion, and anti-oxidant, complement or neutrophil therapy may significantly prevent or limit I-R-induced injury in humans.

Abstract: Platelet-dependent thrombus formation is a key event in the pathogenesis of acute myocardial infarction (AMI). Platelets mediate both thrombotic occlusion of the entire epicardial coronary artery and also accumulate in the microcirculation resulting in impairment of microcirculation and provoking myocardial ischemia during reperfusion. In the past, our understanding of platelet function in myocardial infarction (MI) and reperfusion has extended substantially resulting in development of novel and clinically effective treatment strategies. This review summarizes the mechanisms of coronary thrombosis and consequences of platelet accumulation in reperfused myocardium. Basic pathophysiological mechanisms of platelet adhesion and secretion are reviewed first, followed by the description of the molecular steps involved in platelet-mediated thrombus formation around an atherosclerotic plaque. Next, the role of platelets in inflammation is summarized with the focus on platelet-endothelium and platelet-leukocyte interactions.

Abstract: Reactive oxygen species (ROS) are considered an important factor in ischemia/reperfusion injury to cardiac myocytes. Mitochondrial respiration is an important source of ROS production and hence a potential contributor to cardiac reperfusion injury. In this study, we have examined the effect of ischemia and ischemia followed by reperfusion of rat hearts on various parameters related to mitochondrial function, such as complex I activity, oxygen consumption, ROS production, and cardiolipin content. The activity of complex I was reduced by 25% and 48% in mitochondria isolated from ischemic and reperfused rat heart, respectively, compared with the controls. These changes in complex I activity were associated with parallel changes in state 3 respiration. The capacity of mitochondria to produce H2O2 increased on reperfusion. The mitochondrial content of cardiolipin, which is required for optimal activity of complex I, decreased by 28% and 50% as function of ischemia and reperfusion, respectively. The lower complex I activity in mitochondria from reperfused rat heart could be completely restored to the level of normal heart by exogenous added cardiolipin. This effect of cardiolipin could not be replaced by other phospholipids nor by peroxidized cardiolipin. It is proposed that the defect in complex I activity in ischemic/reperfused rat heart could be ascribed to a ROS-induced cardiolipin damage. These findings may provide an explanation for some of the factors responsible for myocardial reperfusion injury.

Abstract: Background— Prognosis of ischemic cardiomyopathy still remains poor because of the lack of effective treatments. To develop a noninvasive therapy for the disorder, we examined the in vitro and vivo effects of extracorporeal shock wave (SW) that could enhance angiogenesis. Methods and Results— SW treatment applied to cultured human umbilical vein endothelial cells significantly upregulated mRNA expression of vascular endothelial growth factor and its receptor Flt-1 in vitro. A porcine model of chronic myocardial ischemia was made by placing an ameroid constrictor at the proximal segment of the left circumflex coronary artery, which gradually induced a total occlusion of the artery with sustained myocardial dysfunction but without myocardial infarction in 4 weeks. Thereafter, extracorporeal SW therapy to the ischemic myocardial region (200 shots/spot for 9 spots at 0.09 mJ/mm2) was performed (n=8), which induced a complete recovery of left ventricular ejection fraction (51±2% to 62±2%), wall thickening frac...

Abstract: Many changes occur during reperfusion of the myocardium after ischemic damage. Necrosis and apoptosis appear to be ongoing during ischemia, while apoptosis is boosted by the reperfusion event. In the past 10 years, distinct intracellular pathways important for hypertrophy, apoptosis, cardiac failure, ischemic preconditioning and reperfusion damage have been recognized. The eventual response of the cardiomyocyte will depend on energy and time available as well as changes in pH and ion handling and the delicate balance of activation of signaling molecules and transcription factors. There is agreement on the central role of mitochondria and nitric oxide (NO) in programmed cell death. However, although many groups analyzed the contribution of NO to cell death, still the circumstances and levels required for cardioprotection or death are unclear. Growth factors, cytokines, and downstream signaling molecules have been shown to influence programmed cell death through mechanisms reminiscent of preconditioning. Here, the role of apoptosis in ischemia reperfusion-related cell death is reviewed. Important data have been obtained in isolated cells, intact hearts and intact animals. Both pharmacological as well as genetic interventions are discussed. Proof for apoptosis in man post-myocardial infarction (MI) treated through primary Percutaneous Trans-luminal Coronary Angioplasty or other reperfusion therapy is reviewed. Finally, the currently available quantification methods for apoptosis post-MI are mentioned.

Abstract: The chemokine stromal-derived factor-1 (SDF-1, also known as CXCL12) and its receptor CXCR4 have been implicated in homing of stem cells to the bone marrow and the homing of bone marrow-derived cells to sites of injury. Bone marrow cells infiltrate brain and give rise to long-term resident cells following injury. Therefore, SDF-1 and CXCR4 expression patterns in 40 mice were examined relative to the homing of bone marrow-derived cells to sites of ischemic injury using a stroke model. Mice received bone marrow transplants from green fluorescent protein (GFP) transgenic donors and later underwent a temporary middle cerebral artery suture occlusion (MCAo). SDF-1 was associated with blood vessels and cellular profiles by 24 hours through at least 30 days post-MCAo. SDF-1 expression was principally localized to the ischemic penumbra. The majority of SDF-1 expression was associated with reactive astrocytes; much of this was perivascular. GFP+ cells were associated with SDF-1-positive vessels and were also found in the neuropil of regions with increased SDF-1 immunoreactivity. Most vessel-associated GFP+ cells resemble pericytes or perivascular microglia and the majority of the GFP+ cells in the parenchyma displayed characteristics of activated microglial cells. These findings suggest SDF-1 is important in the homing of bone marrow-derived cells, especially monocytes, to areas of ischemic injury.

Abstract: The transcription factor signal transducer and activator of transcription 3 (STAT3) participates in a wide variety of physiological processes and directs seemingly contradictory responses such as proliferation and apoptosis. To elucidate its role in the heart, we generated mice harboring a cardiomyocyte-restricted knockout of STAT3 using Cre/loxP-mediated recombination. STAT3-deficient mice developed reduced myocardial capillary density and increased interstitial fibrosis within the first 4 postnatal months, followed by dilated cardiomyopathy with impaired cardiac function and premature death. Conditioned medium from STAT3-deficient cardiomyocytes inhibited endothelial cell proliferation and increased fibroblast proliferation, suggesting the presence of paracrine factors attenuating angiogenesis and promoting fibrosis in vitro. STAT3-deficient mice showed enhanced susceptibility to myocardial ischemia/reperfusion injury and infarction with increased cardiac apoptosis, increased infarct sizes, and reduced cardiac function and survival. Our study establishes a novel role for STAT3 in controlling paracrine circuits in the heart essential for postnatal capillary vasculature maintenance, interstitial matrix deposition balance, and protection from ischemic injury and heart failure.

Abstract: Objectives— The concept of neovascularization in response to tissue ischemia has been extended by the finding of postnatal vasculogenesis initiated by endothelial progenitor cells (EPCs). The aim of this study was to analyze whether a maximal stress test in patients with coronary artery disease (CAD) increases the number of circulating EPCs. Methods and Results— Blood concentration of EPCs was analyzed by FACS and cell culture assay in CAD patients with (n=16) or without (n=12) exercise-induced myocardial ischemia and in healthy subjects (n=11) for up to 144 hours after maximal stress test. Plasma concentrations of vascular endothelial growth factor (VEGF), basic fibroblast growth factor, tumor necrosis factor-α, and granulocyte macrophage-colony stimulating factor were determined by ELISA. EPCs increased significantly in ischemic patients, with a maximum after 24 to 48 hours (cell culture: 3.3±0.5-fold increase; FACS: 3.1±0.6-fold increase) and returned to baseline within 72 hour. In nonischemic patients and healthy subjects, no EPC increase was detectable. VEGF levels in ischemic patients increased significantly after 2 to 6 hours (maximum after 2 hours; 4.0±1.1-fold increase) and no change was observed in nonischemic patients and healthy subjects; ΔVEGF and ΔEPC correlated significantly ( r =0.66). Conclusions— Patients with symptomatic CAD respond to a single episode of exercise-induced myocardial ischemia with a time-dependent increase in circulating EPCs. This increase may be related to and preceded by an increase in plasma VEGF.

Abstract: Loss of integrity of the blood-brain barrier (BBB) resulting from ischemia and reperfusion is a hypothesized precursor to hemorrhagic transformation (HT) and worse clinical outcome than would be expected from the beneficial effects of reperfusion. We used a novel magnetic resonance imaging marker to characterize early BBB disruption in acute focal brain ischemia and tested associations with reperfusion, HT, and poor outcome (modified Rankin score >2). The BBB disruption was evident as delayed gadolinium enhancement of cerebrospinal fluid space on fluid-attenuated inversion recovery (FLAIR) images and, for convenience, has been termed hyperintense acute reperfusion marker (HARM). HARM was found in 47 of 144 (33%) ischemic stroke patients. Reperfusion was found to be the strongest independent predictor of early BBB disruption (P=0.018) in multivariate analysis. HARM was associated with HT and worse clinical outcome (after adjustment for initial severity). It was also associated with more severe strokes at onset and greater age. Because the timing of the disruption was early enough (median estimate 3.8 hours from onset) to make it relevant to acute thrombolytic therapy, early BBB disruption as defined by HARM may be a promising target for adjunctive therapy to reduce the complications associated with thrombolytic therapy, broaden the therapeutic window, and improve clinical outcome.

Abstract: Background—We recently reported the safety and feasibility of autologous bone marrow mononuclear cell (ABMMNC) injection into areas of ischemic myocardium in patients with end-stage ischemic cardiomyopathy. The present study evaluated the safety and efficacy of this therapy at 6- and 12-month follow-up. Methods and Results—Twenty patients with 6- and 12-month follow-up (11 treated subjects; 9 controls) were enrolled in this prospective, nonrandomized, open-label study. Complete clinical and laboratory evaluations as well as exercise stress (ramp treadmill), 2-dimensional Doppler echocardiography, single-photon emission computed tomography (SPECT) perfusion scanning, and 24-hour Holter monitoring were performed at baseline and follow-up. Transendocardial delivery of ABMMNCs was performed with the aid of electromechanical mapping to identify viable myocardium. Each patient received 15 ABMMNC injections of 0.2 mL each. At 6 and 12 months, total reversible defect, as measured by SPECT perfusion scanning, was significantly reduced in the treatment group as compared with the control group. At 12 months, exercise capacity was significantly improved in the treatment group. This improvement correlated well with monocyte, B-cell, hematopoietic progenitor cell, and early hemapoietic progenitor cell phenotypes. Conclusions—The 6- and 12-month follow-up data in this study suggest that transendocardial injection of ABMMNCs in patients with end-stage ischemic heart disease may produce a durable therapeutic effect and improve myocardial perfusion and exercise capacity. (Circulation. 2004;110[suppl II]:II-213–II-218.)

Abstract: Growing evidence from in vitro studies supports that valproic acid (VPA), an anti-convulsant and mood-stabilizing drug, has neuroprotective effects. The present study investigated whether VPA reduces brain damage and improves functional outcome in a transient focal cerebral ischemia model of rats. Subcutaneous injection of VPA (300 mg/kg) immediately after ischemia followed by repeated injections every 12 h, was found to markedly decrease infarct size and reduce ischemia-induced neurological deficit scores measured at 24 and 48 h after ischemic onset. VPA treatment also suppressed ischemia-induced neuronal caspase-3 activation in the cerebral cortex. VPA treatments resulted in a time-dependent increase in acetylated histone H3 levels in the cortex and striatum of both ipsilateral and contralateral brain hemispheres of middle cerebral artery occlusion (MCAO) rats, as well as in these brain areas of normal, non-surgical rats, supporting the in vitro finding that VPA is a histone deacetylase (HDAC) inhibitor. Similarly, heat shock protein 70 (HSP70) levels were time-dependently up-regulated by VPA in the cortex and striatum of both ipsilateral and contralateral sides of MCAO rats and in these brain areas of normal rats. Altogether, our results demonstrate that VPA is neuroprotective in the cerebral ischemia model and suggest that the protection mechanisms may involve HDAC inhibition and HSP induction.

Abstract: The ischemic penumbra has been documented in the laboratory animal as severely hypoperfused, nonfunctional, but still viable brain tissue surrounding the irreversibly damaged ischemic core. Saving the penumbra is the main target of acute stroke therapy, and is the theoretical basis behind the reperfusion concept. In experimental focal ischemia, early reperfusion has been reported to both prevent infarct growth and aggravate edema formation and hemorrhage, depending on the severity and duration of prior ischemia and the efficiency of reperfusion, whereas neuronal damage with or without enlarged infarction also may result from reperfusion (so-called reperfusion injury). Activated neutrophils contribute to vascular reperfusion damage, yet posthypoxic cellular injury occurs in the absence of inflammatory species. Protein synthesis inhibition occurs in neurons during reperfusion after ischemia, underlying the role that these pathways play in prosurvival and proapoptotic processes that may be differentially expressed in vulnerable and resistant regions of the reperfused brain tissue. Ischemia-induced decreases in the mitochondrial capacity for respiratory activity probably contribute to the ongoing impairment of energy metabolism during reperfusion and possibly also the magnitude of changes seen during ischemia. From these experimental data, the concept of single-drug intervention cannot be effective. Further experimental research is needed, especially of the study of biochemical markers of the injury process to establish the role of several drugs.

Abstract: The current pathophysiological understanding of stroke is substantially based on experimental studies. Brain injury after cerebral ischemia develops from a complex signaling cascade that evolves in an at least partially unraveled spatiotemporal pattern. Early excitotoxicity can lead to fast necrotic cell death, which produces the core of the infarction. The ischemic penumbra that surrounds the infarct core suffers milder insults. In this area, both mild excitotoxic and inflammatory mechanisms lead to delayed cell death, which shows biochemical characteristics of apoptosis. While brain cells are challenged by these deleterious mechanisms, they activate innate protective programs of the brain, which can be studied by means of experimentally inducing ischemic tolerance (i.e., ischemic preconditioning). Importantly, cerebral ischemia not only affects the brain parenchyma, but also impacts extracranial systems. For example, stroke induces a dramatic immunosuppression via an overactivation of the sympathetic nervous system. As a result, severe bacterial infections such as pneumonia occur. Complex signaling cascades not only decide about cell survival, but also about the neurological deficit and the mortality after stroke. These mechanisms of damage and endogenous protection present distinct molecular targets that are the rational basis for the development of neuroprotective drugs.

Abstract: Ischemia-reperfusion (I/R) injury is a common clinical event with the potential to seriously affect, and sometimes kill, the patient. Interruption of blood supply causes ischemia, which rapidly damages metabolically active tissues. Paradoxically, restoration of blood flow to the ischemic tissues initiates a cascade of pathology that leads to additional cell or tissue injury. I/R is a potent inducer of complement activation that results in the production of a number of inflammatory mediators. The use of specific inhibitors to block complement activation has been shown to prevent local tissue injury after I/R. Clinical and experimental studies in gut, kidney, limb, and liver have shown that I/R results in local activation of the complement system and leads to the production of the complement factors C3a, C5a, and the membrane attack complex. The novel inhibitors of complement products may find wide clinical application because there are no effective drug therapies currently available to treat I/R injuries.

Abstract: The neuropathological correlates of encephalopathy and autonomic dysfunction in septic shock are unclear. We performed post mortem analysis of 5 brain areas susceptible to ischemia and 5 autonomic nuclei (AN) in 23 patients who had died in our intensive care unit (ICU) from septic shock and 8 dying from non-septic shock as well as 5 controls who had died suddenly from extracranial injury. Proinflammatory cytokine (IL1-beta and TNF-alpha) and inducible nitric oxide synthase (iNOS) expression was assessed by immunocytochemistry. Abnormalities in septic shock were: hemorrhages (26%), hypercoagulability syndrome (9%), micro-abscesses (9%), multifocal necrotizing leukoencephalopathy (9%) and ischemia (100%). The incidence of cerebral hemorrhage or hypercoagulability syndrome was not related to clotting disturbances. The intensity of ischemia within susceptible areas was the same in both ICU groups, but more pronounced in the autonomic centers of septic patients (P < 0.0001). Neuronal apoptosis assessed using anti-caspase 3 immunocytochemistry and in situ end labeling was more pronounced in the autonomic nuclei of septic patients. (P < 0.0001). TNF-alpha expression did not differ between groups but vascular iNOS expression assessed by immunocytochemistry was higher in sepsis (P<0.0001) and correlated with autonomic center neuronal apoptosis (P < 0.02). We conclude that septic shock is associated with diffuse cerebral damage and specific autonomic neuronal apoptosis which may be due to circulating factors particularly iNOS.