Experimental & Translational Stroke Medicine最新文献

Background: Neuroinflammation evolves as a multi-facetted response to focal cerebral ischemia. It involves activation of resident glia cell populations, recruitment of blood-derived leucocytes as well as humoral responses. Among these processes, phagocyte accumulation has been suggested to be a surrogate marker of neuroinflammation. We previously assessed phagocyte accumulation in human stroke by MRI. We hypothesize that phagocyte accumulation in the macrosphere model may resemble the temporal and spatial patterns observed in human stroke.

Methods: In a rat model of permanent focal ischemia by embolisation of TiO2-spheres we assessed key features of post-ischemic neuroinflammation by the means of histology, immunocytochemistry of glial activation and influx of hematogeneous cells, and quantitative PCR of TNF-α, IL-1, IL-18, and iNOS mRNA.

Results: In the boundary zone of the infarct, a transition of ramified microglia into ameboid phagocytic microglia was accompanied by an up-regulation of MHC class II on the cells after 3 days. By day 7, a hypercellular infiltrate consisting of activated microglia and phagocytic cells formed a thick rim around the ischemic infarct core. Interestingly, in the ischemic core microglia could only be observed at day 7. TNF-α was induced rapidly within hours, IL-1β and iNOS peaked within days, and IL-18 later at around 1 week after ischemia.

Conclusions: The macrosphere model closely resembles the characteristical dynamics of postischemic inflammation previously observed in human stroke. We therefore suggest that the macrosphere model is highly appropriate for studying the pathophysiology of stroke in a translational approach from rodent to human.

Background and purpose: The present study was designed to examine the effects of color stimulation on cerebral blood mean flow velocity (MFV) in men and women.

Methods: The study included 16 (8 men and 8 women) right-handed healthy subjects. The MFV was recorded simultaneously in both right and left middle cerebral arteries in Dark and white Light conditions, and during color (Blue, Yellow and Red) stimulations, and was analyzed using functional transcranial Doppler spectroscopy (fTCDS) technique.

Results: Color processing occurred within cortico-subcortical circuits. In men, wavelength-differencing of Yellow/Blue pairs occurred within the right hemisphere by processes of cortical long-term depression (CLTD) and subcortical long-term potentiation (SLTP). Conversely, in women, frequency-differencing of Blue/Yellow pairs occurred within the left hemisphere by processes of cortical long-term potentiation (CLTP) and subcortical long-term depression (SLTD). In both genders, there was luminance effect in the left hemisphere, while in men it was along an axis opposite (orthogonal) to that of chromatic effect, in women, it was parallel.

Conclusion: Gender-related differences in color processing demonstrated a right hemisphere cognitive style for wavelength-differencing in men, and a left hemisphere cognitive style for frequency-differencing in women. There are potential applications of fTCDS technique, for stroke rehabilitation and monitoring of drug effects.

Background: Several proteins are known to be markedly expressed in the brain during cerebral ischemia; however, the changes in protein profiles within the ischemic brain after an ischemic insult have not been fully elucidated. We studied the changes in the ischemic brain proteome after focal cerebral ischemia, induced by middle cerebral artery occlusion (MCAO) in mice.

Methods: LCMS-IT-TOF mass spectrometry was used to detect the changes in ischemic brain protein patterns after MCAO. We evaluated the protein expression detected in the ischemic area, by western blotting and immunohistochemistry.

Results: Nine unique proteins were identified from the ischemic area at 10 h after ischemic insult. Among these proteins, we focused on Rab33b, a member of RAS oncogene family and we found that Rab33b was up-regulated in the ischemic striatum and the number of Rab33B-positive cells increased in a time-dependent manner. Rab33B colocalized with Iba-1 positive microglia in the ischemic area.

Conclusion: These findings suggest that LCMS-IT-TOF is useful for identifying changes in proteins after cerebral ischemia and that Rab33B is partially related to the pathogenesis of transient cerebral ischemia in mice.

Background: Increased systemic cytokines and elevated brain levels of monoamines, and hydroxyl radical productions are thought to aggravate the conditions of cerebral ischemia and neuronal damage during heat stroke. Dexamethasone (DXM) is a known immunosuppressive drug used in controlling inflammation, and hydroxyethyl starch (HES) is used as a volume-expanding drug in cerebral ischemia and/or cerebral injury. Acute treatment with a combined therapeutic approach has been repeatedly advocated in cerebral ischemia experiments. The aim of this study is to investigate whether the combined agent (HES and DXM) has beneficial efficacy to improve the survival time (ST) and heat stroke-induced cerebral ischemia and neuronal damage in experimental heat stroke.

Methods: Urethane-anesthetized rats underwent instrumentation for the measurement of colonic temperature, mean arterial pressure (MAP), local striatal cerebral blood flow (CBF), heart rate, and neuronal damage score. The rats were exposed to an ambient temperature (43 degrees centigrade) to induce heat stroke. Concentrations of the ischemic and damage markers, dopamine, serotonin, and hydroxyl radical productions in corpus striatum, and the serum levels of interleukin-1 beta, tumor necrosis factor-alpha and malondialdehyde (MDA) were observed during heat stroke.

Results: After heat stroke, the rats displayed circulatory shock (arterial hypotension), decreased CBF, increased the serum levels of cytokines and MDA, increased cerebral striatal monoamines and hydroxyl radical productions release, and severe cerebral ischemia and neuronal damage compared with those of normothermic control rats. However, immediate treatment with the combined agent at the onset of heat stroke confers significant protection against heat stroke-induced circulatory shock, systemic inflammation; cerebral ischemia, cerebral monoamines and hydroxyl radical production overload, and improves neuronal damage and the ST in rats.

Conclusions: Our results suggest that the combination of a colloid substance with a volume-expanding effect and an anti-inflammatory agent may provide a better resuscitation solution for victims with heat stroke.

Background: A major consequence of stroke is permanent motor disturbance, such as postural imbalance and loss of skilled movement. The degree of neuronal and functional loss and subsequent recovery after stroke is influenced by hypothalamic-pituitary-adrenal axis activation and the response to glucocorticoid hormones. This study investigated if recovery after stroke is related to glucocorticoid receptor (GR) activation in a rat model of stroke.

Methods: Adult male rats were pre-trained and tested in a skilled reaching task and received a focal ischemic motor cortex lesion. One group of animals received daily restraint stress starting one week pre-lesion up to three weeks post-lesion. Immuno-histochemical analysis of GR expression was performed to determine receptor activation.

Results: Stress reduced reaching success in naïve animals and diminished recovery of limb use. Exaggerated functional loss in stressed rats was related to increased GR activation in the lesion hemisphere as indicated by nuclear GR location.

Conclusion: These findings provide a mechanistic link between stress-induced motor disability and GR activation in a rat model of stroke. The elevated receptor activation proposes synergistic effects of stress and stroke to modulate the impact of glucocorticoids on motor system function at the genomic level. The modulation of GR biosynthesis may alter responsiveness to stroke treatment and compromise recovery.

Background and purpose: Reliable models are essential for translational stroke research to study the pathophysiology of ischaemic stroke in an effort to find therapies that may ultimately reduce oedema, infarction and mortality in the clinic. The purpose of this study was to investigate the relation between the site of arterial embolization and the subsequent oedema, infarction and clinical outcome in a rat embolic stroke model.

Methods: Thirty-six male Sprague-Dawley rats were thromboembolized into the internal carotid artery. The site of occlusion was demonstrated by arteriography. Following histological preparation and evaluation, the size of the hemispheres and the infarcts were measured by quantitative histology and planimetry. Another parallel stroke model study was subsequently examined to investigate if the conclusions from the first study could be applied to the second study.

Results: The median size of the infarct was 40% of the ipsilateral hemisphere in both the 19 animals with occlusion localised to the intracranial part of the internal carotid artery and in the 11 animals where the main trunk of the middle cerebral artery was occluded. In 5 animals, occlusion of the extracranial part of the internal carotid artery resulted in significantly smaller infarcts compared to other groups (p < 0.01). Another independent study re-confirmed these results. Furthermore, significant correlations (R > 0.76, p < 0.0001) were found between 1) cortical, subcortical, and total infarct volumes, 2) oedema in percent of the left hemisphere, 3) clinical score before termination and 4) postoperative weight loss.

Conclusions: Distal occlusions of the intracranial part of the internal carotid or middle cerebral arteries resulted in comparable large sized infarctions and oedema. This indicates that investigators do not need a similar number of such occlusions in each experimental group. Contrary to observations in the clinic, distal internal carotid artery occlusions did not result in worse outcome than middle cerebral stem occlusions, but this finding may be explained by the controlled emboli size in this experimental stroke model.

Traumatic brain injury, a leading cause of death and disability, is a result of an outside force causing mechanical disruption of brain tissue and delayed pathogenic events which collectively exacerbate the injury. These pathogenic injury processes are poorly understood and accordingly no effective neuroprotective treatment is available so far. Experimental models are essential for further clarification of the highly complex pathology of traumatic brain injury towards the development of novel treatments. Among the rodent models of traumatic brain injury the most commonly used are the weight-drop, the fluid percussion, and the cortical contusion injury models. As the entire spectrum of events that might occur in traumatic brain injury cannot be covered by one single rodent model, the design and choice of a specific model represents a major challenge for neuroscientists. This review summarizes and evaluates the strengths and weaknesses of the currently available rodent models for traumatic brain injury.

Background: Adiponectin is a hormone produced in and released from adipose cells, which has been shown to have anti-diabetic and anti-inflammatory actions in peripheral cells. Two cell surface adiponectin receptors (ADRs) mediate the majority of the known biological actions of adiponectin. Thus far, ADR expression in the brain has been demonstrated in the arcuate and the paraventricular nucleus of hypothalamus, where its activation affects food intake. Recent findings suggest that levels of circulating adiponectin increase after an ischemic stroke, but the role of adiponectin receptor activation in stroke pathogenesis and its functional outcome is unclear.

Methods: Ischemic stroke was induced in C57BL/6 mice by middle cerebral artery occlusion (MCAO) for 1 h, followed by reperfusion. Primary cortical neuronal cultures were established from individual embryonic neocortex. For glucose deprivation (GD), cultured neurons were incubated in glucose-free Locke's medium for 6, 12 or 24 h. For combined oxygen and glucose deprivation (OGD), neurons were incubated in glucose-free Locke's medium in an oxygen-free chamber with 95% N2/5% CO2 atmosphere for either 3, 6, 9, 12 or 24 h. Primary neurons and brain tissues were analysed for Adiponectin and ADRs using reverse transcriptase polymerase chain reaction (RT-PCR), immunoblot and immunochemistry methods.

Results: Cortical neurons express ADR1 and ADR2, and that the levels of ADR1 are increased in neurons in response to in vitro or in vivo ischemic conditions. Neurons treated with either globular or trimeric adiponectin exhibited increased vulnerability to oxygen and glucose deprivation which was associated with increased activation of a pro-apoptotic signaling cascade involving p38 mitogen-activated protein kinase (p38MAPK) and AMP-activated protein kinase (AMPK).

Conclusions: This study reveals a novel pathogenic role for adiponectin and adiponectin receptor activation in ischemic stroke. We show that cortical neurons express ADRs and reveal a pro-apoptotic role for ADR1 activation in neurons, which may render them vulnerable to ischemic death.

Background: Recently, members of the two-pore domain potassium channel family (K2P channels) could be shown to be involved in mechanisms contributing to neuronal damage after cerebral ischemia. K2P3.1-/- animals showed larger infarct volumes and a worse functional outcome following experimentally induced ischemic stroke. Here, we question the role of the closely related K2P channel K2P9.1.

Methods: We combine electrophysiological recordings in brain-slice preparations of wildtype and K2P9.1-/- mice with an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of K2P9.1 in stroke formation.

Results: Patch-clamp recordings reveal that currents mediated through K2P9.1 can be obtained in slice preparations of the dorsal lateral geniculate nucleus (dLGN) as a model of central nervous relay neurons. Current characteristics are indicative of K2P9.1 as they display an increase upon removal of extracellular divalent cations, an outward rectification and a reversal potential close to the potassium equilibrium potential. Lowering extracellular pH values from 7.35 to 6.0 showed comparable current reductions in neurons from wildtype and K2P9.1-/- mice (68.31 +/- 9.80% and 69.92 +/- 11.65%, respectively). These results could be translated in an in vivo model of cerebral ischemia where infarct volumes and functional outcomes showed a none significant tendency towards smaller infarct volumes in K2P9.1-/- animals compared to wildtype mice 24 hours after 60 min of tMCAO induction (60.50 +/- 17.31 mm3 and 47.10 +/- 19.26 mm3, respectively).

Conclusions: Together with findings from earlier studies on K2P2.1-/- and K2P3.1-/- mice, the results of the present study on K2P9.1-/- mice indicate a differential contribution of K2P channel subtypes to the diverse and complex in vivo effects in rodent models of cerebral ischemia.

Stroke is a common cause of permanent disability accompanied by devastating impairments for which there is a pressing need for effective treatment. Motor, sensory and cognitive deficits are common following stroke, yet treatment is limited. Along with histological measures, functional outcome in animal models has provided valuable insight to the biological basis and potential rehabilitation efforts of experimental stroke. Developing and using tests that have the ability to identify behavioral deficits is essential to expanding the development of translational therapies. The present aim of this paper is to review many of the current behavioral tests that assess functional outcome after stoke in rodent models. While there is no perfect test, there are many assessments that are sensitive to detecting the array of impairments, from global to modality specific, after stroke.