Therapeutic hypothermia for acute ischemic stroke: what do laboratory studies teach us?

Effect of a kynurenic acid analog on home-cage activity and body temperature in rats

BACKGROUND

N-(2-N,N-Dimethylaminoethyl)-4-oxo-1H-quinoline-2-carboxamide hydrochloride (SzR-72) is a kynurenic acid (KYNA) amide analog that displays neuroprotective action. Whereas its brain penetration ability and its solubility limit the therapeutic use of KYNA: the corresponding properties of the analog exceed those of the parent compound. Although SzR-72 has been extensively studied, its exact mechanism of action has not yet been fully clarified. As KYNA induces hypothermia in laboratory rodents, it may be hypothesized that SzR-72 may have a similar effect. This would be of major importance, since the hypothermia generated by external cooling is neuroprotective, thus a putative hypothermic effect of SzR-72 could contribute to its neuroprotective action.

METHODS

The effects of SzR-72 on the body temperature and home-cage activity of rats were studied by using a telemetry system. In order to follow the longitudinal changes in the effects of the compound, subchronic drug administration was applied.

RESULTS

The initial administration of the compound induced substantial hypothermia and reduced the home-cage activity. During the 5 days of SzR-72 administration, partial tolerance developed to the hypothermic effect, while the inhibition of home-cage activity detected after the acute administration was completely tolerated.

CONCLUSIONS

On the basis of these results, it cannot be excluded that the hypothermic effect of SzR-72 contributes to its neuroprotective action.

Global SUMOylation is a molecular mechanism underlying hypothermia-induced ischemic tolerance

The molecular mechanisms underlying hypothermic neuroprotection have yet to be fully elucidated. Herein we demonstrate that global SUMOylation, a form of post-translational modification with the Small Ubiquitin-like MOdifer, participates in the multimodal molecular induction of hypothermia-induced ischemic tolerance. Mild (32°C) to moderate (28°C) hypothermic treatment(s) during OGD (oxygen-glucose-deprivation) or ROG (restoration of oxygen/glucose) increased global SUMO-conjugation levels and protected cells (both SHSY5Y and E18 rat cortical neurons) from OGD and ROG-induced cell death. Hypothermic exposure either before or after permanent middle cerebral artery occlusion (pMCAO) surgery in wild type mice increased global SUMO-conjugation levels in the brain and in so doing protected these animals from pMCAO-induced ischemic damage. Of note, hypothermic exposure did not provide an additional increase in protection from pMCAO-induced ischemic brain damage in Ubc9 transgenic (Ubc9 Tg) mice, which overexpress the sole E2 SUMO conjugating enzyme and thereby display elevated basal levels of global SUMOylation under normothermic conditions. Such evidence suggests that increases in global SUMOylation are critical and may account for a substantial part of the observed increase in cellular tolerance to brain ischemia caused via hypothermia.

Combination of therapeutic hypothermia and other neuroprotective strategies after an ischemic cerebral insult

Abrupt deprivation of substrates to neuronal tissue triggers a number of pathological events (the “ischemic cascade”) that lead to cell death. As this is a process of delayed neuronal cell death and not an instantaneous event, several pharmacological and non-pharmacological strategies have been developed to attenuate or block this cascade. The most promising neuroprotectant so far is therapeutic hypothermia and its beneficial effects have inspired researchers to further improve its protective benefit by combining it with other neuroprotective agents. This review provides an overview of all neuroprotective strategies that have been combined with therapeutic hypothermia in rodent models of focal cerebral ischemia. A distinction is made between drugs interrupting only one event of the ischemic cascade from those mitigating different pathways and having multimodal effects. Also the combination of therapeutic hypothermia with hemicraniectomy, gene therapy and protein therapy is briefly discussed. Furthermore, those combinations that have been studied in a clinical setting are also reviewed.

The effect of controlled mild hypothermia on large scald burns in a resuscitated rat model

OBJECTIVE

Early surface cooling of burns reduces pain, depth of injury and improves healing. We hypothesized that controlled mild hypothermia would also prolong survival in a fluid resuscitated rat model of large scald burns.

METHODS

Forty rats were anesthetized and a single full-thickness scald burn covering 40% of total body surface area was created on each of the rats. The rats were then randomized to hypothermia (n=20) or no hypothermia (n=20). Mild hypothermia (a reduction of 2°C) was induced with intraperitoneal 4°C normal saline and ice packs. After 2 hours of hypothermia, the rats were rewarmed back to their baseline temperature with a heating pad. The control rats received room temperature intraperitoneal saline. The difference in survival between the groups was determined using Kaplan-Meier analysis and the log-rank test.

RESULTS

Hypothermia was induced in all experimental rats within a mean of 22 minutes (95% confidence interval, 17 to 27). The number of normothermic and hypothermic rats that expired at each time interval were: at 1 hour, 4 vs. 0; at 10 hours, 2 from each group; at 24 hours, 0 vs. 1; at 48 hours, 2 vs. 2; at 72 hours, 1 vs. 1; and at 120 hours, 1 vs. 1 respectively. There were no differences in time to survival between the groups.

CONCLUSION

Induction of brief, mild hypothermia does not prolong survival in a resuscitated rat model of large scald burns.

Mild hypothermia as a treatment for central nervous system injuries: Positive or negative effects

Besides local neuronal damage caused by the primary insult, central nervous system injuries may secondarily cause a progressive cascade of related events including brain edema, ischemia, oxida-tive stress, excitotoxicity, and dysregulation of calcium homeostasis. Hypothermia is a beneficial strategy in a variety of acute central nervous system injuries. Mild hypothermia can treat high intra-cranial pressure following traumatic brain injuries in adults. It is a new treatment that increases sur-vival and quality of life for patients suffering from ischemic insults such as cardiac arrest, stroke, and neurogenic fever following brain trauma. Therapeutic hypothermia decreases free radical produc-tion, inflammation, excitotoxicity and intracranial pressure, and improves cerebral metabolism after traumatic brain injury and cerebral ischemia, thus protecting against central nervous system dam-age. Although a series of pathological and physiological changes as well as potential side effects are observed during hypothermia treatment, it remains a potential therapeutic strategy for central nervous system injuries and deserves further study.

Limitations of Mild, Moderate, and Profound Hypothermia in Protecting Developing Hippocampal Neurons After Simulated Ischemia

Mild hypothermia (33°C-34°C) after cerebral ischemia in intact animals or ischemia-like conditions in vitro reduces neuron death. However, it is now clear that more profound hypothermia or delayed hypothermia may not provide significant protection. To further define the limitations of hypothermia after cerebral ischemia, we used hippocampal slice cultures to examine the effects of various degrees, durations, and delays of hypothermia on neuron death after an ischemia-like insult. Organotypic cultures of the hippocampus from 7- to 8 day-old rat pups were cooled to 32°C, 23°C, 17°C, or 4°C immediately or after a 2-4 hour delay from an injurious insult of oxygen and glucose deprivation (OGD). Cell death in CA1, CA3 and dentate regions of the cultures was assessed 24 hours later with SYTOX® or propidium iodide, both of which are fluorescent markers labeling damaged cells. OGD caused extensive cell death in CA1, CA3, and dentate regions of the hippocampal cultures. Hypothermia (32°C, 23°C and 17°C) for 4-6 hours immediately after OGD was protective at 24 hours, but when hypothermia was applied for longer periods or delayed after OGD, no protection or increased death was seen. Ultra-profound hypothermia (4°C) increased cell death in all cell areas of the hippocampus even when after a milder insult of only hypoxia. In an in vitro model of recovery after an ischemia-like insult, mild to profound hypothermia is protective only when applied without delay and for limited periods of time (6-8 hours). Longer durations of hypothermia, or delayed application of the hypothermia can increase neuron death. These findings may have implications for clinical uses of therapeutic hypothermia after hypoxic or ischemic insults, and suggest that further work is needed to elucidate the limitations of hypothermia as a protective treatment after ischemic stress.

Moderate hypothermia inhibits brain inflammation and attenuates stroke-induced immunodepression in rats

AIMS

Stroke causes both brain inflammation and immunodepression. Mild-to-moderate hypothermia is known to attenuate brain inflammation, but its role in stroke-induced immunodepression (SIID) of the peripheral immune system remains unknown. This study investigated the effects in rats of moderate intra-ischemic hypothermia on SIID and brain inflammation.

METHODS

Stroke was induced in rats by permanent distal middle cerebral artery occlusion combined with transient bilateral common carotid artery occlusion, while body temperature was reduced to 30°C. Real-time PCR, flow cytometry, in vitro T-cell proliferation assays, in vivo delayed-type hypersensitivity (DTH) reaction and confocal microscopy were used to study SIID and brain inflammation.

RESULTS

Brief intra-ischemic hypothermia helped maintain certain leukocytes in the peripheral blood and spleen and enhanced T-cell proliferation in vitro and delayed-type hypersensitivity in vivo, suggesting that hypothermia reduces SIID. In contrast, in the brain, brief intra-Ischemic hypothermia inhibited mRNA expression of anti-inflammatory cytokine IL-10 and proinflammatory mediators INF-γ, TNF-α, IL-2, IL-1β and MIP-2. Brief intra-Ischemic hypothermia also attenuated the infiltration of lymphocytes, neutrophils (MPO(+) cells) and macrophages (CD68(+) cells) into the ischemic brain, suggesting that hypothermia inhibited brain inflammation.

CONCLUSIONS

Brief intra-ischemic hypothermia attenuated SIID and protected against acute brain inflammation.

Neuroprotective effects of quetiapine on neuronal apoptosis following experimental transient focal cerebral ischemia in rats

OBJECTIVE

This study was undertaken in the belief that the atypical antipsychotic drug quetiapine could prevent apoptosis in the penumbra region following ischemia, taking into account findings that show 5-hydroxytryptamine-2 receptor blockers can prevent apoptosis.

METHODS

We created 5 groups, each containing 6 animals. Nothing was done on the K-I group used for comparisons with the other groups to make sure adequate ischemia had been achieved. The K-II group was sacrificed on the 1st day after transient focal cerebral ischemia and the K-III group on the 3rd day. The D-I group was administered quetiapine following ischemia and sacrificed on the 1st day while the D-II group was administered quetiapine every day following the ischemia and sacrificed on the 3rd day. The samples were stained with the immunochemical TUNEL method and the number of apoptotic cells were counted.

RESULTS

There was a significant difference between the first and third day control groups (K-II/K-III : p=0.004) and this indicates that apoptotic cell death increases with time. This increase was not encountered in the drug groups (D-I/D-II : p=1.00). Statistical analysis of immunohistochemical data revealed that quetiapine decreased the apoptotic cell death that normally increased with time.

CONCLUSION

Quetiapine is already in clinical use and is a safe drug, in contrast to many substances that are used to prevent ischemia and are not normally used clinically. Our results and the literature data indicate that quetiapine could help both as a neuronal protector and to resolve neuropsychiatric problems caused by the ischemia in cerebral ischemia cases.

Metabolic regulatory clues from the naked mole rat: toward brain regulatory functions during stroke

Resistance to tissue hypoxia is a robust fundamental adaptation to low oxygen supply, and represents a novel neuroscience problem with significance to mammalian physiology as well as human health. With the underlying mechanisms strongly conserved in evolution, the ability to resist tissue hypoxia in natural systems has recently emerged as an interesting model in mammalian physiology research to understand mechanisms that can be manipulated for the clinical management of stroke. The extraordinary ability to resist tissue hypoxia by the naked mole rat (NMR) indicates the presence of a unique mechanism that underlies the remarkable healthy life span and exceptional hypoxia resistance. This opens an interesting line of research into understanding the mechanisms employed by the naked mole rat (Heterocephalus glaber) to protect the brain during hypoxia. In a series of studies, we first examined the presence of neuroprotection in the brain cells of naked mole rats (NMRs) subjected to hypoxic insults, and then characterized the expression of such neuroprotection in a wide range of time intervals. We used oxygen nutrient deprivation (OND), an in vitro model of resistance to tissue hypoxia to determine whether there is evidence of neuronal survival in the hippocampal (CA1) slices of NMRs that are subjected to chronic hypoxia. Hippocampus neurons of NMRs that were kept in hypoxic condition consistently tolerated OND right from the onset time of 5h. This tolerance was maintained for 24h. This finding indicates that there is evidence of resistance to tissue hypoxia by CA1 neurons of NMRs. We further examined the effect of hypoxia on metabolic rate in the NMR. Repeated measurement of metabolic rates during exposure of naked mole rats to hypoxia over a constant ambient temperature indicates that hypoxia significantly decreased metabolic rates in the NMR, suggesting that the observed decline in metabolic rate during hypoxia may contribute to the adaptive mechanism used by the NMR to resist tissue hypoxia. This work is aimed to contribute to the understanding of mechanisms of resistance to tissue hypoxia in the NMR as an important life-sustaining process, which can be translated into therapeutic interventions during stroke.

Feasibility of endovascular and surface cooling strategies in acute stroke

BACKGROUND

Therapeutic hypothermia (TH) is a promising treatment of stroke, but limited data are available regarding the safety and effectiveness of cooling methodology. We investigated the safety of TH and compared the cooling capacity of two widely used cooling strategies - endovascular and surface cooling.

METHODS

COOLAID Oresund is a bicentre randomized trial in Copenhagen (Denmark) and Malmö (Sweden). Patients were randomized to either TH (33°C for 24 h) in a general intensive care unit (ICU) or standardized stroke unit care (control). Cooling was induced by a surface or endovascular-based strategy.

RESULTS

Thirty-one patients were randomized. Seven were cooled using endovascular and 10 using surface-based cooling methods and 14 patients received standard care (controls). 14 (45%) patients received thrombolysis. Pneumonia was recorded in 6 (35%) TH patients and in 1 (7%) control. 4 TH patients and 1 control developed massive infarction. 1 TH patient and 2 control suffered asymptomatic haemorrhagic transformation. Mortality was comparable with 2 (12%) in the TH group and 1 (7%) among controls. Mean (SD) duration of hospital stay was 25.0 days (24, 9) in TH and 22.5 days (20.6) in control patients (P = 0.767). Mean (SD) induction period (cooling onset to target temperature) was 126.3 min (80.6) with endovascular cooling and 196.3 min (76.3) with surface cooling (P = 0.025).

CONCLUSIONS

Therapeutic hypothermia with general anaesthesia is feasible in stroke patients. We noticed increased rates of pneumonia, while the length of hospital stay remained comparable. The endovascular cooling strategy provides a faster induction period than surface cooling.

Pre, intra and post-ischemic hypothermic neuroprotection in temporary focal cerebral ischemia in rats: morphometric analysis

OBJECTIVE

To evaluate the neuroprotection of mild hypothermia, applied in different moments, in temporary focal cerebral ischemia in rats.

METHODS

Rats was divided into Control (C), Sham (S), Ischemic-control(IC), Pre-ischemic Hypothermia (IH1), Intra-ischemic Hypothermia (IH2), and Post-ischemic Hypothermia (IH3) groups. Morphometry was performed using the KS400 software (Carl Zeiss®) in coronal sections stained by Luxol Fast Blue. Ischemic areas and volumes were obtained.

RESULTS

Statistically, blue areas showed difference for C vs. IC, IC vs. IH1 and IC vs. IH2 (p=0.0001; p=0.01; p=0.03), and no difference between C vs. S, IC vs. IH3 and IH vs. IH2 (p=0.39; p=0.85; p=0.63). Red areas showed difference between C vs. IC, IC vs. IH1 and IC vs. IH2 (p=0.0001; p=0.009; p=0.03), and no difference between C vs. S, IC vs. IH3 and IH1 vs. IH2 (p=0.48; p=0.27; p=0.68). Average ischemic areas and ischemic volumes showed difference between IC vs. IH1 and IC vs. IH2 (p=0.0001 and p=0.0011), and no difference between IC vs. IH3 and IH1 vs. IH2 (p=0.57; p=0.79).

CONCLUSION

Pre-ischemic and intra-ischemic hypothermia were shown to be similarly neuroprotective, but this was not true for post-ischemic hypothermia.

Hypothermia may attenuate ischemia/reperfusion-induced cardiomyocyte death by reducing autophagy

OBJECTIVE

We sought to assess the effect of therapeutic hypothermia on the autophagy that occurred in ischemia-reperfused (IR) H9c2 cardiomyocytes.

METHODS

In control studies, the H9c2 cells at a density of 1 × 10(5) per culture dish in six-well plate were exposed to normoxic culture medium at 37 °C for 12h. All assays contained appropriate controls and were performed in triplicate and repeated on three separately initiated cultures. In hypothermia-treated group, the ischemic and hypoxic cells were maintained in a 32 °C incubation. The trypan blue exclusion method was used to assess the cell viability. Autophagy was evaluated by determining both the microtubule-associated protein 1 light chain 3 [LC3] levels and punctuate distribution of the autophagic vesicle associated form [LC3-II].

RESULTS

The results were mean ± standard error of mean of triplicates. The viable cell percentage for control group, IR group, and IR group treated with hypothermia at the start of ischemia, or reperfusion were 100% ± 9%, 20% ± 1%, 32% ± 3%, and 41% ± 3%, respectively. The cell death in I/R H9c2 cells was positively associated with increased LC3 levels and punctuate distribution of (LC3-II). Mild hypothermia adopted at the start of ischemia or reperfusion significantly reduced both the cell death and the autophagy in H9c2 cells.

CONCLUSION

Our data indicate that in H9c2, IR stimulates cell autophagy and causes cell death, which can be attenuated by mild hypothermia. Our results, if further confirmed in vivo, may have important clinical implications during IR injury.

Hypothermia protects against oxygen-glucose deprivation-induced neuronal injury by down-regulating the reverse transport of glutamate by astrocytes as mediated by neurons

Glutamate is the major mediator of excitotoxic neuronal death following cerebral ischemia. Under severe ischemic conditions, glutamate transporters can functionally reverse to release glutamate, thereby inducing further neuronal injury. Hypothermia has been shown to protect neurons from brain ischemia. However, the mechanism(s) involved remain unclear. Therefore, the aim of this study was to investigate the mechanism(s) mediating glutamate release during brain ischemia-reperfusion injury under hypothermic conditions. Neuron/astrocyte co-cultures were exposed to oxygen-glucose deprivation (OGD) at various temperatures for 2h, and cell viability was assayed 12h after reoxygenation. PI and MAP-2 staining demonstrated that hypothermia significantly decreased neuronal injury. Furthermore, [(3)H]-glutamate uptake assays showed that hypothermia protected rat primary cortical cultures against OGD reoxygenation-induced injury. Protein levels of the astrocytic glutamate transporter, GLT-1, which is primarily responsible for the clearance of extracellular glutamate, were also found to be reduced in a temperature-dependent manner. In contrast, expression of GLT-1 in astrocyte-enriched cultures was found to significantly increase following the addition of neuron-conditioned medium maintained at 37 °C, and to a lesser extent with neuron-conditioned medium at 33 °C. In conclusion, the neuroprotective effects of hypothermia against brain ischemia-reperfusion injury involve down-regulation of astrocytic GLT-1, which mediates the reverse transport of glutamate. Moreover, this process may be regulated by molecules secreted by stressed neurons.

Mild hypothermia reduces activated caspase-3 up to 1 week after a focal cerebral ischemia induced by endothelin-1 in rats

Hypothermia is a promising neuroprotective therapy that has been shown to reduce apoptosis after an ischemic insult. This study evaluated the effect of mild hypothermia on activated caspase-3 up to 1 week after the induction of a stroke. Endothelin-1 (Et-1) was used to elicit transient focal cerebral ischemia in rats. Twenty minutes after the ischemic insult, a state of mild hypothermia (33°C) was imposed for a duration of 2h. The functional outcome, infarct volume and activated caspase-3 immunoreactivity (IR) were assessed at 8, 24 and 72h, and one week after the insult. During the experiment the cerebral blood flow (CBF) was measured via Laser Doppler Flowmetry. Hypothermia improved the neurological outcome at all of the time points studied compared to the normothermic group, and was associated with a reduction in infarct volume. In both groups, activated caspase-3 IR peaked 24h after the Et-1 induced insult and hypothermia significantly reduced the number of apoptotic cells at 8h, 24h and 1 week after ischemia. Furthermore, the hypothermic treatment did not affect the CBF in the Et-1 model. These findings indicate that in the Et-1 model, hypothermia exerts a long lasting effect on stroke-induced apoptosis.

Hypothermia protects the brain from transient global ischemia/reperfusion by attenuating endoplasmic reticulum response-induced apoptosis through CHOP

Endoplasmic reticulum (ER) stress has been implicated in the pathology of cerebral ischemia. Apoptotic cell death occurs during prolonged period of stress or when the adaptive response fails. Hypothermia blocked the TNF or Fas-mediated extrinsic apoptosis pathway and the mitochondria pathway of apoptosis, however, whether hypothermia can block endoplasmic reticulum mediated apoptosis is never known. This study aimed to elucidate whether hypothermia attenuates brain cerebral ischemia/reperfusion (I/R) damage by suppressing ER stress-induced apoptosis. A 15 min global cerebral ischemia rat model was used in this study. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in hippocampus CA1 were assessed after reperfusion of the brain. The expressions of C/EBP-homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) in ischemic hippocampus CA1 were measured at 6, 12, 24 and 48 h after reperfusion. The results showed that hypothermia significantly attenuated brain I/R injury, as shown by reduction in cell apoptosis, CHOP expression, and increase in GRP78 expression. These results suggest that hypothermia could protect brain from I/R injury by suppressing ER stress-induced apoptosis.

Neuroprotection: lessons from hibernators

Mammals that hibernate experience extreme metabolic states and body temperatures as they transition between euthermia, a state resembling typical warm blooded mammals, and prolonged torpor, a state of suspended animation where the brain receives as low as 10% of normal cerebral blood flow. Transitions into and out of torpor are more physiologically challenging than the extreme metabolic suppression and cold body temperatures of torpor per se. Mammals that hibernate show unprecedented capacities to tolerate cerebral ischemia, a decrease in blood flow to the brain caused by stroke, cardiac arrest or brain trauma. While cerebral ischemia often leads to death or disability in humans and most other mammals, hibernating mammals suffer no ill effects when blood flow to the brain is dramatically decreased during torpor or experimentally induced during euthermia. These animals, as adults, also display rapid and pronounced synaptic flexibility where synapses retract during torpor and rapidly re-emerge upon arousal. A variety of coordinated adaptations contribute to tolerance of cerebral ischemia in these animals. In this review we discuss adaptations in heterothermic mammals that may suggest novel therapeutic targets and strategies to protect the human brain against cerebral ischemic damage and neurodegenerative disease.

Age-related changes in AMP-activated protein kinase after stroke

Adenosine monophosphate-activated protein kinase (AMPK) is an evolutionary conserved energy sensor sensitive to changes in cellular AMP/ATP ratio which is activated by phosphorylation (pAMPK). pAMPK levels decrease in peripheral tissues with age, but whether this also occurs in the aged brain, and how this contributes to the ability of the aged brain to cope with ischemic stress is unknown. This study investigated the activation of AMPK and the response to AMPK inhibition after induced stroke in both young and aged male mice. Baseline levels of phosphorylated AMPK were higher in aged brains compared to young mice. Stroke-induced a robust activation of AMPK in young mice, yet this response was muted in the aged brain. Young mice had larger infarct volumes compared with aged animals; however, more severe behavioral deficits and higher mortality were seen in aged mice after stroke. Inhibition of AMPK with Compound C decreased infarct size in young animals, but had no effect in aged mice. Compound C administration led to a reduction in brain ATP levels and induced hypothermia, which led to enhanced neuroprotection in young but not aged mice. This work demonstrates that aging increases baseline brain pAMPK levels; aged mice have a muted stroke-induced pAMPK response; and that AMPK inhibition and hypothermia are less efficacious neuroprotective agents in the aged brain. This has important translational relevance for the development of neuroprotective agents in preclinical models and our understanding of the enhanced metabolic stress experienced by the aged brain.

[Intensive care management [corrected] of patients with intracerebral hemorrhage]

Approximately 10-15% of acute strokes are caused by non-aneurysmatic intracerebral hemorrhage (ICH) and incidences are expected to increase due to an aging population. Studies from the 1990s estimated mortality of ICH to be as high as 50%. However, these figures may partly be attributed to the fact that patients suffering from ICH frequently received only supportive therapy and the poor prognosis may therefore be more a self-fulfilling prophecy. Recently it has been shown that treatment in a specialized neurological intensive care unit alone was associated with better outcomes after ICH. In recent years considerable efforts have been undertaken in order to develop new therapies for ICH and to assess them in randomized controlled trials. Apart from admission status, hemorrhage volume is considered to be the main prognostic factor and impeding the spread of the hematoma is thus a basic therapeutic principle. The use of activated factor VIIa (aFVIIa) to stop hematoma enlargement has been assessed in two large randomized controlled trials, however the promising results of the dose-finding study could not be confirmed in a phase III trial. Although hemostatic therapy with aFVIIa reduced growth of the hematoma it failed to improve clinical outcome. Similar results were found in a randomized controlled trial on blood pressure management in acute ICH. The link between reduction of hematoma growth and improved outcome is therefore still lacking. Likewise the value of surgical hematoma evacuation remains uncertain. In the largest randomized controlled trial on surgical treatment in ICH so far, only a small subgroup of patients with superficial hemorrhages seemed to benefit from hematoma evacuation. Whether improved intensive care can contribute to improved outcome after ICH will be shown by data obtained in the coming years.

Experimental and clinical use of therapeutic hypothermia for ischemic stroke: opportunities and limitations

Stroke remains a disease with a serious impact on quality of life but few effective treatments exist. There is an urgent need to develop and/or improve neuroprotective strategies to combat this. Many drugs proven to be neuroprotective in experimental models fail to improve patient outcome in a clinical setting. An emerging treatment, therapeutic hypothermia (TH), is a promising neuroprotective therapy in stroke management. Several studies with TH in experimental models and small clinical trials have shown beneficial effects. Despite this, implementation into the clinical setting is still lacking due to methodological considerations as well as hypothermia-related complications. This paper discusses the possible opportunities and limitations of the use of TH in animal models and the translation into the clinic.

Potassium-induced structural changes of the endoplasmic reticulum in pyramidal neurons in murine organotypic hippocampal slices

The endoplasmic reticulum (ER) structure is of central importance for the regulation of cellular anabolism, stress response, and signal transduction. Generally continuous, the ER can temporarily undergo dramatic structural rearrangements resulting in a fragmented appearance. In this study we assess the dynamic nature of ER fission in pyramidal neurons in organotypic hippocampal slice cultures stimulated by depolarizing concentration of potassium (50 mM). The slices were obtained from transgenic mice expressing fluorescent ER-targeted DsRed2 protein. We employed live tissue confocal microscopy imaging with fluorescence recovery after photobleaching (FRAP) to monitor the extent of structural rearrangements of the ER. In control slices, the ER structure was continuous. Potassium stimulation resulted in extensive fragmentation (fission), whereas return to basal potassium levels (2.5 mM) led to ER fusion and normalization of ER structure. This ER fission/fusion could be repeated several times in the same neuron, demonstrating the reversibility of the process. Blockade of the N-methyl-D-aspartate receptor (NMDAR) with the antagonist D-AP5 or removal of extracellular Ca(2+) prevented depolarization-induced ER fission. ER fission is sensitive to temperature, and decreasing temperature from 35°C to 30°C augments fission, implying that the altering of ER continuity may be a protective response against damage. We conclude that events that generate membrane depolarisation in brain tissue lead to the release of endogenous glutamate that may regulate neuronal ER continuity. The rapid and reversible NMDAR-mediated changes in ER structure reflect an adaptive, innate property of the ER for synaptic activation as well as response to tissue stress, injury, and disease.

Mild Hypothermia Attenuates Intercellular Adhesion Molecule-1 Induction via Activation of Extracellular Signal-Regulated Kinase-1/2 in a Focal Cerebral Ischemia Model

Intercellular adhesion molecule-1 (ICAM-1) in cerebral vascular endothelium induced by ischemic insult triggers leukocyte infiltration and inflammatory reaction. We investigated the mechanism of hypothermic suppression of ICAM-1 in a model of focal cerebral ischemia. Rats underwent 2 hours of middle cerebral artery occlusion and were kept at 37°C or 33°C during occlusion and rewarmed to normal temperature immediately after reperfusion. Under hypothermic condition, robust activation of extracellular signal-regulated kinase-1/2 (ERK1/2) was observed in vascular endothelium of ischemic brain. Hypothermic suppression of ICAM-1 was reversed by ERK1/2 inhibition. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) in ischemic vessel was attenuated by hypothermia. STAT3 inhibitor suppressed ICAM-1 production induced by stroke. ERK1/2 inhibition enhanced phosphorylation and DNA binding activity of STAT3 in hypothermic condition. In this study, we demonstrated that hypothermic suppression of ICAM-1 induction is mediated by enhanced ERK1/2 activation and subsequent attenuation of STAT3 action.

Controlled mild hypothermia prolongs survival in a rat model of large scald burns

OBJECTIVES

Early surface cooling of burns reduces pain and depth of injury and improves healing. However, there are concerns that cooling of large burns may result in hypothermia and worsen outcomes. In contrast, controlled mild hypothermia improves outcomes after cardiac arrest and traumatic brain injury. The authors hypothesized that controlled mild hypothermia would prolong survival in a rat model of large scald burns.

METHODS

Thirty-six Sprague-Dawley rats (250-300 g) were anesthetized with 40 mg/kg intramuscular ketamine and 5 mg/kg xylazine, with supplemental inhalational isoflurane as needed. A single full-thickness scald burn covering 40% of total body surface area was created on each of the rats using a Mason-Walker template placed in boiling water (100 °C) for a period of 10 seconds. The rats were then randomized to hypothermia (n = 18) or no hypothermia (n = 18). Core body temperature was continuously monitored with a rectal temperature probe. In the experimental group, mild hypothermia was induced by applying ice packs over the prone rats until their rectal temperature was reduced by 2 °C for a period of 2 hours. After 2 hours of hypothermia, the rats were rewarmed back to their baseline temperature with a heating pad. The control rats were not cooled. The rats were monitored until death or for a period of 7 days, whichever was greater. The primary outcome was time to death. The difference in survival between the groups was determined using Kaplan-Meier analysis and the log-rank test.

RESULTS

  Hypothermia was induced in all experimental rats within a mean of 22 minutes (95% confidence interval [CI] = 17 to 27). The numbers of nonhypothermic and hypothermic rats that were dead at each time point were as follows: 2 hours, five versus none; 18 hours, 16 versus five; 24 hours, 18 versus eight; and 48 hours, 18 versus 13 (p = 0.05). There were no additional deaths after 48 hours. The mean time to survival of the hypothermic rats was significantly greater than that of the nonhypothermic rats (p < 0.001).

CONCLUSIONS

Induction of brief, mild hypothermia prolongs survival and increases the survival rate in nonresuscitated rats with large scald burns.

Current proceedings of childhood stroke

Stroke is a sudden onset neurological deficit due to a cerebrovascular event. In children, the recognition of stroke is often delayed due to the low incidence of stroke and the lack of specific assessment measures to this entity. The causes of pediatric stroke are significantly different from that of adult stroke. The lack of safety and efficiency data in the treatment is the challenge while facing children with stroke. Nearly half of survivors of pediatric stroke may have neurologic deficits affecting functional status and quality of life. They may cause a substantial burden on health care resources. Hence, an accurate history, including onset and duration of symptoms, risk factors, and a complete investigation, including hematologic, neuroimaging, and metabolic studies is the key to make a corrective diagnosis. A prompt and optimal treatment without delay may minimize the damage to the brain.

Mild-to-moderate neurogenic pyrexia in acute cerebral infarction

BACKGROUND

Pyrexia is often associated with unfavorable stroke outcomes. However, limited information is available on the relationship between the causes of poststroke hyperthermia and stroke prognosis, especially for mild-to-moderate neurogenic pyrexia in acute cerebral infarction.

AIMS

To compare the differences in the clinical features and characteristics of pyrexia as well as its prognosis among acute cerebral infarction patients with mild-to-moderate neurogenic pyrexia, with infectious pyrexia, and without pyrexia. The focus was on mild-to-moderate neurogenic pyrexia.

METHODS

A total of 709 patients with acute cerebral infarction were prospectively recruited and their clinical data were analyzed.

RESULTS

No significant difference was detected in age, gender, history of smoking, hypertension, or diabetes among the 3 groups (p > 0.05). Patients with mild-to-moderate neurogenic pyrexia and those with infectious pyrexia had higher baseline National Institutes of Health Stroke Scale (NIHSS) scores (15.1 ± 6.7, p = 0.003; 14.3 ± 8.1, p = 0.002, respectively), lower 3-month Barthel index (BI) values (64.2 ± 40.7, p < 0.001; 61.9 ± 49.3, p < 0.001, respectively) and higher 3-month mortality rates (13%, p = 0.026; 16%, p < 0.001, respectively) than patients without pyrexia (NIHSS score 11.4 ± 7.9; BI 82.6 ± 39.8, and mortality rate 6%, respectively). No difference existed in these parameters between the 2 pyrexia groups (p > 0.05), but mild-to-moderate neurogenic pyrexia had an earlier onset and a shorter duration than infectious pyrexia (p < 0.001).

CONCLUSIONS

Acute cerebral infarction patients with mild-to-moderate neurogenic pyrexia had a similar prognosis compared to those with infectious pyrexia. Mild-to-moderate neurogenic pyrexia is possibly associated with stroke severity.

Attenuation of brain nitrostative and oxidative damage by brain cooling during experimental traumatic brain injury

The aim of the present study was to ascertain whether brain cooling causes attenuation of traumatic brain injury by reducing brain nitrostative and oxidative damage. Brain cooling was accomplished by infusion of 5 mL of 4°C saline over 5 minutes via the external jugular vein. Immediately after the onset of traumatic brain injury, rats were randomized into two groups and given 37°C or 4°C normal saline. Another group of rats were used as sham operated controls. Behavioral and biochemical assessments were conducted on 72 hours after brain injury or sham operation. As compared to those of the sham-operated controls, the 37°C saline-treated brain injured animals displayed motor deficits, higher cerebral contusion volume and incidence, higher oxidative damage (e.g., lower values of cerebral superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase, but higher values of cerebral malondialdehyde), and higher nitrostative damage (e.g., higher values of neuronal nitric oxide synthase and 3-nitrotyrosine). All the motor deficits and brain nitrostative and oxidative damage were significantly reduced by retrograde perfusion of 4°C saline via the jugular vein. Our data suggest that brain cooling may improve the outcomes of traumatic brain injury in rats by reducing brain nitrostative and oxidative damage.

Modeling focal cerebral ischemia in vivo

Ischemic stroke is among the leading causes of mortality and long-term disability in the western world. Despite enormous research activities in the last decades, current therapeutic options for acute stroke patients are still very limited. Reliable and realistic in vivo animal models represent sine qua non for -successful translation from bench to bedside. To date, several animal models of focal and global cerebral ischemia have been developed to mimic the clinical situation in humans as accurately as possible. This chapter focuses on models of focal cerebral ischemia, in particular on the most commonly used model: the intraluminal filament model of middle cerebral artery occlusion. The main objective is to provide a detailed instruction manual for researchers interested in learning this technique.

Induction of mild hypothermia by noninvasive body cooling in healthy, unanesthetized subjects

The induction of mild hypothermia has been considered as an important means to provide protection against cerebral ischemia. Yet, to date, the relative clinical efficacies of different noninvasive methods for reducing core body temperature have not been thoroughly studied. The aim of the current investigation was to compare the relative effectiveness of several noninvasive cooling techniques for reducing core temperatures in healthy volunteers. Cooling methods included convective/conductive and evaporative/conductive combinations, as well as evaporative cooling alone. Additionally, focal facial warming was employed as a means to suppress involuntary motor activity and thus better enable noninvasive cooling. Core temperatures were measured so to monitor the relative efficiencies of these induced cooling methodologies. With each employed methodology, rectal temperature reductions were induced, with combined evaporative/conductive (n=4, 1.44°C±0.99°C) and convective/conductive (n=4, 1.51°C±0.89°C) approaches yielding the largest decreases: note, that evaporative cooling alone was not as efficient in lowering core body temperature (n=10, 0.56°C±0.20°C; n=16, 0.58°C±0.27°C). In this study on healthy volunteers, the evaporative/conductive and convective/conductive combination methods were more effective in reducing core temperatures as compared with an evaporative approach alone. These therapeutic approaches for the induction of mild hypothermia (including the use of facial warming) could be employed in warranted clinical cases, importantly without the need for administration of anesthetics or paralytics.

State of the art in therapeutic hypothermia

Historically, hypothermia was induced prior to surgery to enable procedures with prolonged ischemia, such as open heart surgery and organ transplant. Within the past decade, the efficacy of hypothermia to treat emergency cases of ongoing ischemia such as stroke, myocardial infarction, and cardiac arrest has been studied. Although the exact role of ischemia/reperfusion is unclear clinically, hypothermia holds significant promise for improving outcomes for patients suffering from reperfusion after ischemia. Research has elucidated two distinct windows of opportunity for clinical use of hypothermia. In the early intra-ischemia window, hypothermia modulates abnormal cellular free radical production, poor calcium management, and poor pH management. In the more delayed post-reperfusion window, hypothermia modulates the downstream necrotic, apoptotic, and inflammatory pathways that cause delayed cell death. Improved cooling and monitoring technologies are required to realize the full potential of this therapy. Herein we discuss the current state of clinical practice, clinical trials, recommendations for cooling, and ongoing research on therapeutic hypothermia.

Mild hypothermia reduces ischemic neuron death via altering the expression of p53 and bcl-2

OBJECTIVE

Studies exploring roles of p53 and bcl-2 in neuroprotection by hypothermia in focal cerebral ischemia have not provided consistent results. In the present study, we determined whether p53 and bcl-2 are involved in the hypothermia-induced neuroprotection.

METHODS

Male Sprague-Dawley rats were divided into four groups: normothermic (37-38 degrees C) ischemia, hypothermic (31-32 degrees C) ischemia, hyperthermic (41-42 degrees C) ischemia and sham-operated group. Global cerebral ischemia was established for 20 minutes using the Pulsinelli four-vessel occlusion model and the brain temperature was maintained at defined levels for 60 minutes following the 20 min ischemia. The mortality in rats was evaluated at 72 hour and 168 hour reperfusion. The expression of p53 and bcl-2 proteins was detected at 24, 48 and 72 hours after reperfusion. At the same intervals, neuron necrosis and apoptosis in brain regions was also detected using hematoxylin and eosin (HE) staining and terminal deoxynucleotldyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL).

RESULTS

The mortalities of rats in normothemia, hypothermia and hyperthermia groups was 33.3, 16.7 and 50% at 72 hour reperfusion. At 168 hours of reperfusion, the mortality in the three groups was 58.3, 25 and 100%, respectively. In light microscopy studies, necrotic neurons and apoptotic neurons were found in the hippocampus after global cerebral ischemia. Surviving neurons in hippocampus was increased in mild hypothermic ischemia group (p<0.05) and decreased in hyperthermia ischemia group (p<0.01) at 24, 48 and 72 hour reperfusion. TUNEL-positive neurons in hippocampus decreased in hypothermic ischemia group (p<0.05 or p<0.01) and increased in hyperthermic ischemia group (p<0.01) at 24, 48 and 72 hour reperfusion. The expression of p53 and bcl-2 proteins was found in the neurons of cerebral cortex after global cerebral ischemia. P53 decreased and bcl-2 increased in hypothermia group.

CONCLUSION

Hypothermia reduces ischemic neuronal necrosis and apoptosis by reducing p53 and increasing bcl-2 expression. Hyperthermia accelerated ischemic neuronal injury by increasing p53 and reducing bcl-2 expression.

Therapeutic hypothermia for brain ischemia: where have we come and where do we go?

Mild hypothermia is an established neuroprotectant in the laboratory, showing remarkable and consistent effects across multiple laboratories and models of brain injury. At the clinical level, mild hypothermia has shown benefits in patients who have experienced cardiac arrest and in some pediatric populations experiencing hypoxic brain insults. Its role, however, in stroke therapy has yet to be established. Translating preclinical data to the clinical arena presents unique challenges with regard to cooling in patients who are generally awake and may require additional therapies, such as reperfusion. We review the state of therapeutic hypothermia in ischemic and hemorrhagic stroke and provide an outlook for its role in stroke therapy.

Inhibition of acute lung inflammation and injury is a target of brain cooling after heatstroke injury

BACKGROUND

Although brain cooling has recently been reported as effective in improving the survival after heatstroke generation in rats, the mechanisms underlying the therapeutic effects of brain cooling are not fully elucidated. This study was conducted to test whether the acute lung inflammation and damage that might occur during heatstroke could be affected by brain cooling.

METHODS

Anesthetized rats were randomized into four groups as follows: (a) normothermic controls (n = 8); (b) heatstroke rats without saline delivery (n = 8); (c) heatstroke rats treated with 36°C saline via retrograde jugular vein (n = 8); and (d) heatstroke rats treated with 4°C saline via retrograde jugular vein (n = 8). Heatstroke was induced by putting the animals in a folded heating pad of 42°C for 68 minutes controlled by circulating hot water. The core temperatures of normothermic groups were maintained at about 36°C. The cardiovascular parameters and core temperatures were monitored for all experiments. Bronchoalveolar lavage (BAL) was done in the left lung 20 minutes after termination of heat stress for determination of cellular ischemia markers (e.g., glutamate, lactate-to-pyruvate ratio), proinflammatory cytokines (interleukin-1, tumor necrosis factor-alpha), and nitric oxide metabolites. Parts of the right lung were excised for meloperoxidase measurement, whereas the rest was collected for lung damage score assessments.

RESULTS

When compared with those of normothermic controls, untreated or 36°C saline-treated heatstroke rats had higher values of BAL fluid levels of cellular ischemia markers, proinflammatory cytokines, nitric oxide metabolites, lung meroperoxidase activity, lung damage score, and neutrophil infiltration. Brain cooling causes by 4°C saline infusion significantly reduced the heat-induced increased BAL levels of cellular ischemia markers, proinflammatory cytokines, and nitric oxide metabolites, and reduced lung damage score and neutrophil infiltration.

CONCLUSIONS

These experimental data indicate that acute lung inflammation and damage is a target of brain cooling after heatstroke injury.

Too cold may not be so cool: spontaneous hypothermia as a marker of poor outcome after cardiac arrest

In a recent issue of Critical Care, den Hartog and colleagues show an association between spontaneous hypothermia, defined by an admission body temperature <35°C, and poor outcome in patients with coma after cardiac arrest (CA) treated with therapeutic hypothermia (TH). Given that TH alters neurological prognostication, studies aiming to identify early markers of injury severity and outcome are welcome, since they may contribute overall to optimize the management of comatose CA patients. This study provides an important message to clinicians involved in post-resuscitation care and raises important questions that need to be taken into account in future studies.

The association between hypothermia, prehospital cooling, and mortality in burn victims

OBJECTIVES

Hypothermia is associated with increased morbidity and mortality in trauma victims. The prognostic value of hypothermia on emergency department (ED) presentation in burn victims is not well known. The objective of this study was to determine the incidence of hypothermia in burn victims and its association with mortality and hospital length of stay (LOS). The study also examined the potential causative role of prehospital cooling in hypothermic burn patients.

METHODS

This was a retrospective review of a county trauma registry. The county was both suburban and rural, with a population of 1.5 million and with one burn center. Burn patients between 1994 and 2007 who met trauma registry criteria were included. Demographic and clinical data including prehospital cooling, burn size and depth, and presence of inhalation injury were collected. Hypothermia was defined as a core body temperature of less than or equal to 35 degrees C. Data analysis consisted of univariate associations between patient characteristics and hypothermia.

RESULTS

There were 1,215 burn patients from 1994 to 2007. Mean age (+/-standard deviation [+/-SD]) was 29 (+/-24) years, 67% were male, 248 (26.7%) had full-thickness burns, and 24 (2.6%) had inhalation injury. Only 17 (1.8%) had a burn larger than 70% total body surface area (TBSA). A total of 929 (76%) patients had an initial ED temperature recorded. Only 15/929 (1.6%) burn patients had hypothermia on arrival, and all were mild (lowest temperature was 32.6 degrees C). There was no association between sex, year, and presence of inhalation injury with hypothermia. Hypothermic patients were older (44 years vs. 29 years, p = 0.01), and median Injury Severity Score (ISS) was higher (25 vs. 4, p = 0.002) than for nonhypothermic patients. Hypothermia was present in 6/17 (35%) patients with a TBSA of 70% or greater and in 8/869 (0.9%) patients with a TBSA of <70% (p < 0.001). Mortality was higher in hypothermic patients (60% vs. 3%, p < 0.001). None of the hypothermic patients received prehospital cooling.

CONCLUSIONS

Hypothermia on presentation to the ED was noted in 1.6% of all burn victims in this trauma registry. Hypothermia was more common in very large burns and was associated with high mortality. In this series, prehospital cooling did not appear to contribute to hypothermia.

Hypothermia as a cytoprotective strategy in ischemic tissue injury

Hypothermia is a well established cytoprotectant, with remarkable and consistent effects demonstrated across multiple laboratories. At the clinical level, it has recently been shown to improve neurological outcome following cardiac arrest and neonatal hypoxia-ischemia. It is increasingly being embraced by the medical community, and could be considered an effective neuroprotectant. Conditions such as brain injury, hepatic encephalopathy and cardiopulmonary bypass seem to benefit from this intervention. It's role in direct myocardial protection is also being explored. A review of the literature has demonstrated that in order to appreciate the maximum benefits of hypothermia, cooling needs to begin soon after the insult, and maintained for relatively long period periods of time. In the case of ischemic stroke, cooling should ideally be applied in conjunction with the re-establishment of cerebral perfusion. Translating this to the clinical arena can be challenging, given the technical challenges of rapidly and stably cooling patients. This review will discuss the application of hypothermia especially as it pertains to its effects neurological outcome, cooling methods, and important parameters in optimizing hypothermic protection.

Combined neuroprotective modalities coupled with thrombolysis in acute ischemic stroke: a pilot study of caffeinol and mild hypothermia

BACKGROUND

Both caffeinol and hypothermia are neuroprotective in preclinical models of transient middle cerebral artery occlusion. We tested whether combining caffeinol and hypothermia with tissue plasminogen activator (t-PA) in patients with acute stroke is safe and feasible.

METHODS

Twenty patients with acute ischemic stroke were treated with caffeinol (caffeine 8-9 mg/kg + ethanol 0.4 g/kg intravenously [IV] x 2 hours, started by 4 hours after symptom onset) and hypothermia (started by 5 hours and continued for 24 hours [target temperature 33-35 degrees C] followed by 12 hours of rewarming). IV t-PA was given to eligible patients. Meperidine and buspirone were used to suppress shivering.

RESULTS

All patients received caffeinol, and most reached target blood levels. Cooling was attempted in 18 patients via endovascular (n = 8) or surface (n = 10) approaches. Two patients were not cooled due to catheter or machine failure. Thirteen patients reached target temperature; average time from symptom onset was 9 hours and 43 minutes. The last 5 hypothermia patients received surface cooling with iced saline induction and larger doses of meperidine; all patients reached target temperature, on average within 2 hours and 30 minutes from induction and 6 hours and 21 minutes from symptom onset. Three patients died: one from symptomatic hemorrhage, one from malignant cerebral edema, and one from unrelated medical complications. No adverse events were attributed to caffeinol. One patient had reduced respiratory drive due to meperidine, requiring BiPAP.

DISCUSSION

Combining caffeinol with hypothermia in patients with acute stroke given IV t-PA is feasible. A prospective placebo-controlled randomized study is needed to further assess safety and to test the efficacy of caffeinol, hypothermia, or both.

Validation of housekeeping genes for quantitative real-time PCR in in-vivo and in-vitro models of cerebral ischaemia

Background

Studies of gene expression in experimental cerebral ischaemia models can contribute to understanding the pathophysiology of brain ischaemia and to identifying prognostic markers and potential therapeutic targets. The normalization of relative qRT-PCR data using a suitable reference gene is a crucial prerequisite for obtaining reliable conclusions. No validated housekeeping genes have been reported for the relative quantification of the mRNA expression profile activated in in-vitro ischaemic conditions, whereas for the in-vivo model different reference genes have been used.

The present study aims to determine the expression stability of ten housekeeping genes (Gapdh, β2m, Hprt, Ppia, Rpl13a, Oaz1, 18S rRNA, Gusb, Ywhaz and Sdha) to establish their suitability as control genes for in-vitro and in-vivo cerebral ischaemia models.

Results

The expression stability of the candidate reference genes was evaluated using the 2^-ΔC'T method and ANOVA followed by Dunnett's test. For the in-vitro model using primary cultures of rat astrocytes, all genes analysed except for Rpl13a and Sdha were found to have significantly different levels of mRNA expression. These different levels were also found in the case of the in-vivo model of pMCAO in rats except for Hprt, Sdha and Ywhaz mRNA, where the expression did not vary. Sdha and Ywhaz were identified by geNorm and NormFinder as the two most stable genes.

Conclusion

We have validated endogenous control genes for qRT-PCR analysis of gene expression in in-vitro and in-vivo cerebral ischaemia models. For normalization purposes, Rpl13a and Sdha are found to be the most suitable genes for the in-vitro model and Sdha and Ywhaz for the in-vivo model. Genes previously used as housekeeping genes for the in-vivo model in the literature were not validated as good control genes in the present study, showing the need for careful evaluation for each new experimental setup.

Early brain temperature elevation and anaerobic metabolism in human acute ischaemic stroke

Early after acute ischaemic stroke, elevation of brain temperature might augment tissue metabolic rate and conversion of ischaemic but viable tissue to infarction. This might explain the observed link between pyrexia, severe stroke and poor outcome. We tested this hypothesis by measuring brain temperature and lactate concentration with multi-voxel magnetic resonance spectroscopic imaging across the acute ischaemic stroke lesion and normal brain as determined on diffusion imaging. We compared patterns of lactate concentration (reported in 'institutional units') and temperature elevation in diffusion lesion core, potential penumbra, ipsilateral and contralateral normal brain and with stroke severity. Amongst 40 patients with moderate to severe acute stroke imaged up to 26 h after onset, lactate concentration was highest in the ischaemic lesion core (42 versus 26 units in potential penumbra, P < 0.05), whereas temperature was highest in the potential penumbra (37.7 versus 37.3 degrees C in lesion core, P < 0.05). Neither sub-regional temperature nor lactate concentration correlated with stroke severity. With increasing time after stroke, ipsilateral brain temperature did not change, but contralateral hemisphere temperature was higher in patients scanned at later times; lactate remained elevated in the lesion core, but declined in potential penumbral and ipsilateral normal tissue at later times. We conclude that early brain temperature elevation after stroke is not directly related to lactate concentration, therefore augmented metabolism is unlikely to explain the relationship between early pyrexia, severe stroke and poor outcome. Early brain temperature elevation may result from different mechanisms to those which raise body temperature after stroke. Further studies are required to determine why early brain temperature elevation is highest in potential penumbral tissue.