Effects of moderate hypothermia on IL-1 beta-induced leukocyte rolling and adhesion in pial microcirculation of mice and on proinflammatory gene expression in human cerebral endothelial cells

Genetic Polymorphisms, Gene-Gene Interactions and Neurologic Sequelae at Two Years Follow-Up in Newborns with Hypoxic-Ischemic Encephalopathy Treated with Hypothermia

Inflammation and oxidative stress after hypoxic-ischemic brain injury may be modified by genetic variability in addition to therapeutic hypothermia. The aim of our study was to evaluate the association between the polymorphisms in genes of antioxidant and inflammatory pathways in newborns treated with therapeutic hypothermia and the development of epilepsy or CP at two years follow-up. The DNA of 55 subjects was isolated from buccal swabs. Genotyping using competitive allele-specific PCR was performed for polymorphisms in antioxidant (SOD2 rs4880, CAT rs1001179, GPX1 rs1050450) and inflammatory (NLRP3 rs35829419, CARD8 rs2043211, IL1B rs1143623, IL1B rs16944, IL1B rs10716 76, TNF rs1800629) pathways. Polymorphic CARD8 rs2043211 T allele was less frequent in patients with epilepsy, but the association was not statistically significant. The interaction between CARD8 rs2043211 and IL1B rs16944 was associated with epilepsy after HIE: CARD8 rs2043211 was associated with lower epilepsy risk, but only in carriers of two normal IL1B rs16944 alleles (OR_adj = 0.03 95% CI = 0.00–0.55; p_adj = 0.019). Additionally, IL1B rs16944 was associated with higher epilepsy risk only in carriers of at least one polymorphic CARD8 rs2043211 (OR_adj = 13.33 95% CI = 1.07–166.37; p_adj = 0.044). Our results suggest that gene–gene interaction in inflammation pathways might contribute to the severity of brain injury in newborns with HIE treated with therapeutic hypothermia.

Inflammatory Regulation of CNS Barriers After Traumatic Brain Injury: A Tale Directed by Interleukin-1

Several barriers separate the central nervous system (CNS) from the rest of the body. These barriers are essential for regulating the movement of fluid, ions, molecules, and immune cells into and out of the brain parenchyma. Each CNS barrier is unique and highly dynamic. Endothelial cells, epithelial cells, pericytes, astrocytes, and other cellular constituents each have intricate functions that are essential to sustain the brain's health. Along with damaging neurons, a traumatic brain injury (TBI) also directly insults the CNS barrier-forming cells. Disruption to the barriers first occurs by physical damage to the cells, called the primary injury. Subsequently, during the secondary injury cascade, a further array of molecular and biochemical changes occurs at the barriers. These changes are focused on rebuilding and remodeling, as well as movement of immune cells and waste into and out of the brain. Secondary injury cascades further damage the CNS barriers. Inflammation is central to healthy remodeling of CNS barriers. However, inflammation, as a secondary pathology, also plays a role in the chronic disruption of the barriers' functions after TBI. The goal of this paper is to review the different barriers of the brain, including (1) the blood-brain barrier, (2) the blood-cerebrospinal fluid barrier, (3) the meningeal barrier, (4) the blood-retina barrier, and (5) the brain-lesion border. We then detail the changes at these barriers due to both primary and secondary injury following TBI and indicate areas open for future research and discoveries. Finally, we describe the unique function of the pro-inflammatory cytokine interleukin-1 as a central actor in the inflammatory regulation of CNS barrier function and dysfunction after a TBI.

CARD8 and IL1B Polymorphisms Influence MRI Brain Patterns in Newborns with Hypoxic-Ischemic Encephalopathy Treated with Hypothermia

Inflammation and oxidative stress are recognized as important contributors of brain injury in newborns due to a perinatal hypoxic-ischemic (HI) insult. Genetic variability in these pathways could influence the response to HI and the outcome of brain injury. The aim of our study was to evaluate the impact of common single-nucleotide polymorphisms in the genes involved in inflammation and response to oxidative stress on brain injury in newborns after perinatal HI insult based on the severity and pattern of magnetic resonance imaging (MRI) findings. The DNA of 44 subjects was isolated from buccal swabs. Genotyping was performed for NLRP3 rs35829419, CARD8 rs2043211, IL1B rs16944, IL1B rs1143623, IL1B rs1071676, TNF rs1800629, CAT rs1001179, SOD2 rs4880, and GPX1 rs1050450. Polymorphism in CARD8 was found to be protective against HI brain injury detected by MRI overall findings. Polymorphisms in IL1B were associated with posterior limb of internal capsule, basal ganglia, and white matter brain patterns determined by MRI. Our results suggest a possible association between genetic variability in inflammation- and antioxidant-related pathways and the severity of brain injury after HI insult in newborns.

A temperature-dependent conformational shift in p38α MAPK substrate-binding region associated with changes in substrate phosphorylation profile

Febrile-range hyperthermia worsens and hypothermia mitigates lung injury, and temperature dependence of lung injury is blunted by inhibitors of p38 mitogen-activated protein kinase (MAPK). Of the two predominant p38 isoforms, p38α is proinflammatory and p38β is cytoprotective. Here, we analyzed the temperature dependence of p38 MAPK activation, substrate interaction, and tertiary structure. Incubating HeLa cells at 39.5 °C stimulated modest p38 activation, but did not alter tumor necrosis factor-α (TNFα)-induced p38 activation. In in vitro kinase assays containing activated p38α and MAPK-activated kinase-2 (MK2), MK2 phosphorylation was 14.5-fold greater at 39.5 °C than at 33 °C. By comparison, we observed only 3.1- and 1.9-fold differences for activating transcription factor-2 (ATF2) and signal transducer and activator of transcription-1α (STAT1α) and a 7.7-fold difference for p38β phosphorylation of MK2. The temperature dependence of p38α:substrate binding affinity, as measured by surface plasmon resonance, paralleled substrate phosphorylation. Hydrogen-deuterium exchange MS (HDX-MS) of p38α performed at 33, 37, and 39.5 °C indicated temperature-dependent conformational changes in an α helix near the common docking and glutamate:aspartate substrate-binding domains at the known binding site for MK2. In contrast, HDX-MS analysis of p38β did not detect significant temperature-dependent conformational changes in this region. We observed no conformational changes in the catalytic domain of either isoform and no corresponding temperature dependence in the C-terminal p38α-interacting region of MK2. Because MK2 participates in the pathogenesis of lung injury, the observed changes in the structure and function of proinflammatory p38α may contribute to the temperature dependence of acute lung injury.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Reconsidering the role of decompressive craniectomy for neurological emergencies

OBJECTIVE

There is little doubt that decompressive craniectomy can reduce mortality. However, there is concern that any reduction in mortality comes at an increase in the number of survivors with severe neurological disability.

METHOD

Over the past decade there have been several randomised controlled trials comparing surgical decompression with standard medical therapy in the context of ischaemic stroke and severe traumatic brain injury. The results of each trial are evaluated.

RESULTS

There is now unequivocal evidence that a decompressive craniectomy reduces mortality in the context of "malignant" middle infarction and following severe traumatic brain injury. However, it has only been possible to demonstrate an improvement in outcome by categorizing a mRS of 4 and upper severe disability as favourable outcome. This is contentious and an alternative interpretation is that surgical decompression reduces mortality but exposes a patient to a greater risk of survival with severe disability.

CONCLUSION

It would appear unlikely that further randomised controlled trials will be possible given the significant reduction in mortality achieved by surgical decompression. It may be that observational cohort studies and outcome prediction models may provide data to determine those patients most likely to benefit from surgical decompression.

Influence of hypothermia and subsequent rewarming upon leukocyte-endothelial interactions and expression of Junctional-Adhesion-Molecules A and B

Patients with risks of ischemic injury, e.g. during circulatory arrest in cardiac surgery, or after resuscitation are subjected to therapeutic hypothermia. For aortic surgery, the body is traditionally cooled down to 18 °C and then rewarmed to body temperature. The role of hypothermia and the subsequent rewarming process on leukocyte-endothelial interactions and expression of junctional-adhesion-molecules is not clarified yet. Thus, we investigated in an in-vitro model the influence of temperature modulation during activation and transendothelial migration of leukocytes through human endothelial cells. Additionally, we investigated the expression of JAMs in the rewarming phase. Exposure to low temperatures alone during transmigration scarcely affects leukocyte extravasation, whereas hypothermia during treatment and transendothelial migration improves leukocyte-endothelial interactions. Rewarming causes a significant up-regulation of transmigration with falling temperatures. JAM-A is significantly modulated during rewarming. Our data suggest that transendothelial migration of leukocytes is not only modulated by cell-activation itself. Activation temperatures and the rewarming process are essential. Continued hypothermia significantly inhibits transendothelial migration, whereas the rewarming process enhances transmigration strongly. The expression of JAMs, especially JAM-A, is strongly modulated during the rewarming process. Endothelial protection prior to warm reperfusion and mild hypothermic conditions reducing the difference between hypothermia and rewarming temperatures should be considered.

Risk Factors Associated With Surgical Site Infection After Pediatric Posterior Spinal Fusion Procedure

Objective.

To identify risk factors associated with surgical site infection (SSI) after pediatric posterior spinal fusion procedure by examining characteristics related to the patient, the surgical procedure, and tissue hypoxia.

Design.

Retrospective case-control study nested in a hospital cohort study.

Setting.

A 475-bed, tertiary care children's hospital.

Methods.

All patients who underwent a spinal fusion procedure during the period from January 1995 through December 2006 were included. SSI cases were identified by means of prospective surveillance using National Nosocomial Infection Surveillance system definitions. Forty-four case patients who underwent a posterior spinal fusion procedure and developed an SSI were identified and evaluated. Each case patient was matched (on the basis of date of surgery, ± 3 months) to 3 control patients who underwent a posterior spinal fusion procedure but did not develop an SSI. Risk factors for SSI were evaluated by univariate analysis and multivariable conditional logistic regression. Odds ratios (ORs), with 95% confidence intervals (CIs) andPvalues, were calculated.

Results.

From 1995 to 2006, the mean annual rate of SSI after posterior spinal fusion procedure was 4.4% (range, 1.1%—6.7%). Significant risk factors associated with SSI in the univariate analysis included the following: a body mass index (BMI) greater than the 95th percentile (OR, 3.5 [95% CI, 1.5–8.3]); antibiotic prophylaxis with clindamycin, compared with other antibiotics (OR, 3.5 [95% CI, 1.2 10.0]); inappropriately low dose of antibiotic (OR, 2.6 [95% CI, 1.0–6.6]); and a longer duration of hypothermia (ie, a core body temperature of less than 35.5°C) during surgery (OR, 0.4 [95% CI, 0.2–0.9]). An American Society of Anesthesiologists (ASA) score of greater than 2, obesity (ie, a BMI greater than the 95th percentile), antibiotic prophylaxis with clindamycin, and hypothermia were statistically significant in the multivariable model.

Conclusion.

An ASA score greater than 2, obesity, and antibiotic prophylaxis with clindamycin were independent risk factors for SSI. Hypothermia during surgery appears to provide protection against SSI in this patient population.

Hypothermia induced by adenosine 5'-monophosphate attenuates injury in an L-arginine-induced acute pancreatitis rat model

BACKGROUND AND AIM

This study sought to investigate the effects of hypothermia induced by adenosine 5'-monophosphate (5'-AMP) on L-arginine (L-Arg)-induced acute pancreatitis in rats.

METHODS

The rats were divided into four groups: the control group, the acute pancreatitis group, the 5'-AMP pretreatment group, and the 5'-AMP posttreatment group. Rats in all groups, except for the control group, received two injections of 2.5 g/kg body weight (intraperitoneally) L-Arg, with an interval of 1 h between the injections. Subsequently, the rats were observed to assess whether hypothermia induced by 5'-AMP could effectively inhibit inflammation associated with L-Arg-induced acute pancreatitis in rats.

RESULTS

Hypothermia induced by 5'-AMP produced protective effects in our acute pancreatitis model. These effects exhibited the following manifestations: (i) a significant reduction in rat mortality rates; (ii) a significant decrease in the occurrence of pancreatic edema; (iii) significant reductions in serum amylase (P < 0.001), interleukin-6 (P < 0.001), interleukin-1β (P < 0.001) and tumor necrosis factor-α (P < 0.001); (iv) the significant inhibition of nuclear factor-κB (NF-κB) activation in rats that were pre- and posttreated with 5'-AMP compared with rats that were only injected with L-Arg; and (v) significant decreases in the occurrence of pancreatic interstitial edema, inflammatory cell infiltration, hemorrhage, and acinar cell necrosis.

CONCLUSIONS

Hypothermia induced by 5'-AMP could inhibit the acute inflammatory reaction and NF-κB activation associated with acute pancreatitis.

1H nuclear magnetic resonance brain metabolomics in neonatal mice after hypoxia-ischemia distinguished normothermic recovery from mild hypothermia recoveries

BACKGROUND

Mild brain hypothermia (31-34 °C) after neonatal hypoxia-ischemia (HI) improves neurodevelopmental outcomes in human and animal neonates. Using an asphyxia model with neonatal mice treated with mild hypothermia after HI, we investigated whether (1)H nuclear magnetic resonance (NMR) metabolomics of brain extracts could suggest biomarkers and distinguish different treatments and outcome groups.

METHODS

At postnatal day 7 (P7), CD1 mice underwent right carotid artery occlusion, 30 min of HI (8% oxygen), and 3.5 h of either hypothermia (31 °C) or normothermia (37 °C). Whole brains were frozen immediately after HI, immediately after 3.5 h of hypothermia or normothermia treatments, and 24 h later. Perchloric acid extractions of 36 metabolites were quantified by 900 MHz (1)H NMR spectroscopy. Multivariate analyses included principal component analyses (PCA) and a novel regression algorithm. Histological injury was quantified after HI at 5 d.

RESULTS

PCA scores plots separated normothermia/HI animals from hypothermia/HI and control animals, but more data are required for multivariate models to be predictive. Loadings plots identified 11 significant metabolites, whereas the regression algorithm identified 6. Histological injury scores were significantly reduced by hypothermia.

CONCLUSION

Different treatment and outcome groups are identifiable by (1)H NMR metabolomics in a neonatal mouse model of mild hypothermia treatment of HI.

Acute and delayed protective effects of pharmacologically induced hypothermia in an intracerebral hemorrhage stroke model of mice

Hemorrhagic stroke, including intracerebral hemorrhage (ICH), is a devastating subtype of stroke; yet, effective clinical treatment is very limited. Accumulating evidence has shown that mild to moderate hypothermia is a promising intervention for ischemic stroke and ICH. Current physical cooling methods, however, are less efficient and often impractical for acute ICH patients. The present investigation tested pharmacologically induced hypothermia (PIH) using the second-generation neurotensin receptor (NTR) agonist HPI-201 (formerly known as ABS-201) in an adult mouse model with ICH. Acute or delayed administrations of HPI-201 (2mg/kg bolus injection followed by 2 injections of 1mg/kg, i.p.) were initiated at 1 or 24h after ICH. HPI-201 induced mild hypothermia within 30 min and body and brain temperatures were maintained at 32.7 ± 0.4°C for at least 6h without causing observable shivering. With the 1-h delayed treatment, HPI-201-induced PIH significantly reduced ICH-induced cell death and brain edema compared to saline-treated ICH animals. When HPI-201-induced hypothermia was initiated 24h after the onset of ICH, it still significantly attenuated brain edema, cell death and blood-brain barrier breakdown. HPI-201 significantly decreased the expression of matrix metallopeptidase-9 (MMP-9), reduced caspase-3 activation, and increased Bcl-2 expression in the ICH brain. Moreover, ICH mice received 1-h delayed HPI-201 treatment performed significantly better in the neurological behavior test 48 h after ICH. All together, these data suggest that systemic injection of HPI-201 is an effective hypothermic strategy that protects the brain from ICH injury with a wide therapeutic window. The protective effect of this PIH therapy is partially mediated through the alleviation of apoptosis and neurovascular damage. We suggest that pharmacological hypothermia using the newly developed neurotensin analogs is a promising therapeutic treatment for ICH.

Hypothermia for neuroprotection in children after cardiopulmonary arrest

BACKGROUND

Cardiopulmonary arrest in paediatric patients often results in death or survival with severe brain injury. Therapeutic hypothermia, lowering of the core body temperature to 32°C to 34°C, may reduce injury to the brain in the period after the circulation has been restored. This therapy has been effective in neonates with hypoxic ischaemic encephalopathy and adults after witnessed ventricular fibrillation cardiopulmonary arrest. The effect of therapeutic hypothermia after cardiopulmonary arrest in paediatric patients is unknown.

OBJECTIVES

To assess the clinical effectiveness of therapeutic hypothermia after paediatric cardiopulmonary arrest.

SEARCH METHODS

We searched the Cochrane Anaesthesia Review Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 11); Ovid MEDLINE (1966 to December 2011); Ovid EMBASE (1980 to December 2011); Ovid CINAHL (1982 to December 2011); Ovid BIOSIS (1923 to December 2011); and Web of Science (1945 to December 2011). We searched the trials registry databases for ongoing trials. We also contacted international experts in therapeutic hypothermia and paediatric critical care to locate further published and unpublished studies.

SELECTION CRITERIA

We planned to include randomized and quasi-randomized controlled trials comparing therapeutic hypothermia with normothermia or standard care in children, aged 24 hours to 18 years, after paediatric cardiopulmonary arrest.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed articles for inclusion.

MAIN RESULTS

We found no studies that satisfied the inclusion criteria. We found four on-going randomized controlled trials which may be available for analysis in the future. We excluded 18 non-randomized studies. Of these 18 non-randomized studies, three compared therapeutic hypothermia with standard therapy and demonstrated no difference in mortality or the proportion of children with a good neurological outcome; a narrative report was presented.

AUTHORS' CONCLUSIONS

Based on this review, we are unable to make any recommendations for clinical practice. Randomized controlled trials are needed and the results of on-going trials will be assessed when available.

Time-dependent effects of hypothermia on microglial activation and migration

Background

Therapeutic hypothermia is one of the neuroprotective strategies that improve neurological outcomes after brain damage in ischemic stroke and traumatic brain injury. Microglial cells become activated following brain injury and play an important role in neuroinflammation and subsequent brain damage. The aim of this study was to determine the time-dependent effects of hypothermia on microglial cell activation and migration, which are accompanied by neuroinflammation.

Methods

Microglial cells in culture were subjected to mild (33 °C) or moderate (29 °C) hypothermic conditions before, during, or after lipopolysaccharide (LPS) or hypoxic stimulation, and the production of nitric oxide (NO), proinflammatory cytokines, reactive oxygen species, and neurotoxicity was evaluated. Effects of hypothermia on microglial migration were also determined in in vitro as well as in vivo settings.

Results

Early-, co-, and delayed-hypothermic treatments inhibited microglial production of inflammatory mediators to varying degrees: early treatment was the most efficient, and delayed treatment showed time-dependent effects. Delayed hypothermia also suppressed the mRNA levels of proinflammatory cytokines and iNOS, and attenuated microglial neurotoxicity in microglia-neuron co-cultures. Furthermore, delayed hypothermia reduced microglial migration in the Boyden chamber assay and wound healing assay. In a stab injury model, delayed local hypothermia reduced migration of microglia toward the injury site in the rat brain.

Conclusion

Taken together, our results indicate that delayed hypothermia is sufficient to attenuate microglial activation and migration, and provide the basis of determining the optimal time window for therapeutic hypothermia. Delayed hypothermia may be neuroprotective by inhibiting microglia-mediated neuroinflammation, indicating the therapeutic potential of post-injury hypothermia for patients with brain damages exhibiting some of the inflammatory components.

Facts and fiction: the impact of hypothermia on molecular mechanisms following major challenge

Numerous multiple trauma and surgical patients suffer from accidental hypothermia. While induced hypothermia is commonly used in elective cardiac surgery due to its protective effects, accidental hypothermia is associated with increased posttraumatic complications and even mortality in severely injured patients. This paper focuses on protective molecular mechanisms of hypothermia on apoptosis and the posttraumatic immune response. Although information regarding severe trauma is limited, there is evidence that induced hypothermia may have beneficial effects on the posttraumatic immune response as well as apoptosis in animal studies and certain clinical situations. However, more profound knowledge of mechanisms is necessary before randomized clinical trials in trauma patients can be initiated.

Hypothermia and pediatric cardiac arrest

The survival outcome following pediatric cardiac arrest still remains poor. Survival to hospital discharge ranges anywhere from 0 to 38% when considering both out-of-hospital and in-hospital arrests, with up to 50% of the survivors having neurologic injury. The use of mild induced hypothermia has not been definitively proven to improve outcomes following pediatric cardiac arrest. This may be due to the lack of consensus regarding target temperature, best method of cooling, optimal duration of cooling and identifying the patient population who will receive the greatest benefit. We review the current applications of induced hypothermia in pediatric patients following cardiac arrest after searching the current literature through Pubmed and Ovid journal databases. We put forth compiled recommendations/guidelines for initiating hypothermia therapy, its maintenance, associated monitoring and suggested adjunctive therapies to produce favorable neurologic and survival outcomes.

Alterations in blood-brain barrier permeability to large and small molecules and leukocyte accumulation after traumatic brain injury: effects of post-traumatic hypothermia

We investigated the temporal and regional profile of blood-brain barrier (BBB) permeability to both large and small molecules after moderate fluid percussion (FP) brain injury in rats and determined the effects of post-traumatic modest hypothermia (33 degrees C/4 h) on these vascular perturbations. The visible tracers biotin-dextrin-amine 3000 (BDA-3K, 3 kDa) and horseradish peroxidase (HRP, 44 kDa) were injected intravenously at 4 h or 3 or 7 days post-TBI. At 30 min after the tracer infusion, both small and large molecular weight tracers were detected in the contusion area as well as remote regions adjacent to the injury epicenter in both cortical and hippocampal structures. In areas adjacent to the contusion site, increased permeability to the small molecular weight tracer (BDA-3K) was evident at 4 h post-TBI and remained visible after 7 days survival. In contrast, the larger tracer molecule (HRP) appeared in these remote areas at acute permeable sites but was not detected at later post-traumatic time periods. A regionally specific relationship was documented at 3 days between the late-occurring permeability changes observed with BDA-3K and the accumulation of CD68-positive macrophages. Mild hypothermia initiated 30 min after TBI reduced permeability to both large and small tracers and the infiltration of CD68-positive cells. These results indicate that moderate brain injury produces temperature-sensitive acute, as well as more long-lasting vascular perturbations associated with secondary injury mechanisms.

Hypothermia increases interleukin-6 and interleukin-10 in juvenile endotoxemic mice

OBJECTIVE

To develop a juvenile mouse model to establish effects of in vivo hypothermia on expression of the inflammation-modulating cytokines tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and interleukin-10. Although induced hypothermia is neuroprotective in some patients, the mechanisms of protection are not well understood and concerns remain over potential detrimental effects, particularly in the setting of infection. We previously showed that in vitro hypothermia increases production of tumor necrosis factor-alpha and interleukin-1beta in lipopolysaccharide-treated monocytes.

DESIGN

: Laboratory investigation.

SETTING

Research laboratory.

SUBJECTS

Juvenile (4-wk) male C57BL/6 mice.

INTERVENTIONS

: Mice were given chlorpromazine to suspend thermoregulation and lipopolysaccharide to stimulate cytokine production. Core temperature was maintained at 32 degrees C or 37 degrees C for 6 hrs by adjusting environmental temperature. In separate experiments, lipopolysaccharide-treated mice were kept in a cooling chamber without chlorpromazine treatment.

MEASUREMENTS AND MAIN RESULTS

Plasma and organs were collected for cytokine quantitation. Chlorpromazine-treated hypothermic mice had 2.3-fold and 1.8-fold higher plasma interleukin-6 and interleukin-10 levels at 6 hrs compared with identically treated normothermic mice (p < .05), whereas plasma tumor necrosis factor-alpha and interleukin-1beta were not significantly different at 2 hrs or 6 hrs. Liver tumor necrosis factor-alpha and interleukin-6 were significantly higher in hypothermic vs. normothermic mice, but lung and brain cytokines were not different. Lipopolysaccharide-treated mice kept in a cooling chamber without chlorpromazine treatment developed varying degrees of hypothermia with associated increases in plasma interleukin-6 and interleukin-10. A nonspecific marker of stress (plasma corticosterone) was not affected by hypothermia in lipopolysaccharide-treated mice.

CONCLUSION

Further studies are necessary to determine the mechanism and physiologic consequences of augmented systemic interleukin-6 and interleukin-10 expression during induced hypothermia.

Post-ischemic hypothermia attenuates loss of the vascular basement membrane proteins, agrin and SPARC, and the blood-brain barrier disruption after global cerebral ischemia

Vascular basement membrane (BM) stabilizes brain vessels and inhibits endothelial cell cycle. Cerebral ischemia causes BM breakdown with the loss of structural BM components including collagens and laminins. In this study, the expression changes of the BM proteoglycan agrin, and the non-structural BM constituent SPARC (BM-40, osteonectin), were studied in brain vessels after global cerebral ischemia. A transient 20-min forebrain ischemia followed by 1, 6 or 24 h of reperfusion was induced in adult Sprague-Dawley rats by combined bilateral common carotid artery occlusion and hypotension (42-45 mm Hg). In a separate group of animals, a mild (32 degrees C) post-ischemic hypothermia was induced for 6 h, starting immediately after ischemia. RNA from approximately 500 brain vessels (20-100 microm) extracted by laser-capture microdissection (LCM) microscopy was used to determine the expression of proteoglycans agrin and SPARC mRNAs by quantitative PCR (Q-PCR). Protein expression was determined by immunohistochemistry in adjacent tissue sections. The BBB permeability was assessed using (3)H-sucrose as an in vivo tracer and by examining fibrinogen immunoreactivity in tissue sections. A transient global brain ischemia resulted in a significant (ANOVA, p<0.05; 6 animals/group) reduction in agrin and SPARC mRNAs in LCM-captured brain vessels 24 h after reperfusion. A time-dependent loss of agrin and SPARC from the BM during reperfusion was also observed by immunochemistry. A 6-h post-ischemic hypothermia reduced SPARC and agrin mRNA and protein losses, BBB transfer constant for (3)H-sucrose as well as fibrinogen extravasation 24 h after reperfusion. It is conluded that a transient post-ischemic hypothermia stabilizes brain vessels and reduces BBB disruption in part by preventing proteolytic degradation of regulatory BM constituents, SPARC and agrin.

Hypothermia therapy after pediatric cardiac arrest

BACKGROUND

Hypothermia therapy improves mortality and functional outcome after cardiac arrest and birth asphyxia in adults and newborns. The effect of hypothermia therapy in infants and children with cardiac arrest is unknown.

METHODS AND RESULTS

A 2-year, retrospective, 5-center study was conducted, and 222 patients with cardiac arrest were identified. Seventy-nine (35.6%) of these patients met eligibility criteria for the study (age >40 weeks postconception and <18 years, cardiac arrest >3 minutes in duration, survival for > or = 12 hours after return of circulation, and no birth asphyxia). Twenty-nine (36.7%) of these 79 patients received hypothermia therapy and were cooled to 33.7+/-1.3 degrees C for 20.8+/-11.9 hours. Hypothermia therapy was associated with higher mortality (P=0.009), greater duration of cardiac arrest (P=0.005), more resuscitative interventions (P<0.001), higher postresuscitation lactate levels (P<0.001), and use of extracorporeal membrane oxygenation (P<0.001). When adjustment was made for duration of cardiac arrest, use of extracorporeal membrane oxygenation, and propensity scores by use of a logistic regression model, no statistically significant differences in mortality were found (P=0.502) between patients treated with hypothermia therapy and those treated with normothermia. Also, no differences in hypothermia-related adverse events were found between groups.

CONCLUSIONS

Hypothermia therapy was used in resuscitation scenarios that are associated with greater risk of poor outcome. In an adjusted analysis, the effectiveness of hypothermia therapy was neither supported nor refuted. A randomized controlled trial is needed to rigorously evaluate the benefits and harms of hypothermia therapy after pediatric cardiac arrest.

Hypothermia augments NF-kappaB activity and the production of IL-12 and IFN-gamma

BACKGROUND

The differentiation of Th1 and Th2 is strictly regulated by humoral and cellular factors. The imbalance between Th1 and Th2 is considered to be the pathogenesis of allergic and autoimmune disorders. It is important to elucidate the effect of environmental factors, such as temperature, on the expression of cytokines of Th1 and Th2.

METHODS

We investigated the expression of IFN-gamma, IL-4, IL-5, IL-10 and IL-12 from LPS- or PHA-stimulated PBMCs at 30 degrees C or 37 degrees C using ELISA and Real-time PCR. We measured the change of NF-kappaB activity at 30 degrees C or 37 degrees C with LPS stimulation using the reporter gene assay.

RESULTS

IFN-gamma production from LPS-stimulated PBMCs at 30 degrees C was up-regulated compared with 37 degrees C. IL-5 and IL-10 production from PHA-stimulated PBMCs at 30 degrees C were down-regulated compared with 37 degrees C. This augmented IFN-gamma production was caused by the up-regulation of IL-12 production from CD14+ blood monocytes. Both IL-12 mRNA and IL12 protein at 30 degrees C were up-regulated compared with 37 degrees C. NF-kappaB, the key molecule for the expression of IL-12, was also augmented at 30 degrees C compared with 37 degrees C.

CONCLUSIONS

Hypothermia up-regulated the expression of IL-12 and IFN-gamma due to the augmented NF-kappaB activity. It is suggested that hypothermia modifies the pattern of cytokine gene expression.

Hypothermia therapy for cardiac arrest in pediatric patients

Cardiac arrest is associated with high morbidity and mortality in children. Hypothermia therapy has theoretical benefits on brain preservation and has the potential to decrease morbidity and mortality in children following cardiac arrest. The American Heart Association guidelines recommend that it should be considered in children after cardiac arrest. Methods of inducing hypothermia include simple surface cooling techniques, intravenous boluses of cold saline, gastric lavage with ice-cold normal saline, and using the temperature control device with extracorporeal life support. We recommend further study before a strong recommendation can be made to use hypothermia therapy in children with cardiac arrest.

Use of induced hypothermia for neuroprotection: indications and application

Therapeutic temperature regulation has become an exciting field of interest. Mild-to-moderate hypothermia is a safe and feasible management strategy for neuroprotection and control of intracranial pressure in neurological catastrophies such as traumatic brain injury, subarachnoid and intracerebral hemorrhage, and large hemispheric stroke. Fever is associated with worse neurological outcome in patients with brain injury, normothermia may be of benefit in this patient population. The efficacy of mild-to-moderate hypothermia has been proven for neuroprotection after cardiac arrest with ventricular fibrillation as initial rhythm, and after neonatal asphyxia. Application of hypothermia and fever control in neurocritical care, available cooling technologies and systemic effects and complications of hypothermia will be discussed.

Differential in vivo potential of endothelial progenitor cells from human umbilical cord blood and adult peripheral blood to form functional long-lasting vessels

Tissue engineering requires formation of a de novo stable vascular network. Because of their ability to proliferate, differentiate into endothelial cells, and form new vessels, blood-derived endothelial progenitor cells (EPCs) are attractive source of cells for use in engineering blood vessels. However, the durability and function of EPC-derived vessels implanted in vivo are unclear. To this end, we directly compared formation and functions of tissue-engineered blood vessels generated by peripheral blood- and umbilical cord blood-derived EPCs in a model of in vivo vasculogenesis. We found that adult peripheral blood EPCs form blood vessels that are unstable and regress within 3 weeks. In contrast, umbilical cord blood EPCs form normal-functioning blood vessels that last for more than 4 months. These vessels exhibit normal blood flow, perm-selectivity to macromolecules, and induction of leukocyte-endothelial interactions in response to cytokine activation similar to normal vessels. Thus, umbilical cord blood EPCs hold great therapeutic potential, and their use should be pursued for vascular engineering.

The effects of hypothermia on endotoxin-primed lung

BACKGROUND

Hypothermia may be effective for endotoxin-induced acute lung injury. In most studies, hypothermia was induced before the development of neutrophilic inflammation, which would be clinically irrelevant. We investigated whether hypothermia induced after the onset of such neutrophilic inflammation reduces acute lung injury.

METHODS

In the first experiment, rats were allocated to one of four groups: intratracheal saline instillation/killed at 1 h (saline), intratracheal lipopolysaccharide (LPS) instillation/killed at 1 h (LPS-primed), intratracheal LPS instillation/killed at 6 h (LPS-NT), all under normothermia (NT) (37 +/- 0.5 degrees C) throughout study, and intratracheal LPS instillation/killed at 6 h with hypothermia (HT) (32 +/- 0.5 degrees C) for the last 5 h of study (LPS-HT). Lungs were lavaged for biochemical measurements. In the second experiment in 26 additional rats, we followed exactly the same protocol as described above for the saline group (n = 2), LPS-NT (n = 12), and LPS-HT (n = 12), and obtained a fresh pool of alveolar neutrophils to assess oxidative burst.

RESULTS

Compared with the LPS-primed group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and myeloperoxidase activity of the lung were all higher in the LPS-NT group. Compared with this LPS-NT group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and microscopic scores for alveolar neutrophilic infiltration were all lower in the LPS-HT group. The stimulated production of hydrogen peroxide in neutrophils was lower in the LPS-HT group than in the LPS-NT group.

CONCLUSION

Hypothermia, applied even after the onset of neutrophilic inflammation, was effective in reducing endotoxin-induced acute lung injury.

Interleukin-1 as a therapeutic target in acute brain injury

Interest in the interactions between the immune and central nervous systems has furthered our understanding of brain function in health and disease. Experimental and clinical studies increasingly reveal an inflammatory component in the pathophysiology of many forms of brain injury. Members of the interleukin (IL)-1 cytokine family are produced by diverse cell types within the brain and may determine the outcome of neuronal injury. This review discusses the neuroprotective potential of IL-1 inhibition in various acute neurological and neurosurgical diseases. The ILs comprise an expanding family of cytokines with diverse physiological and pathological actions, of which IL-1 is a key inflammatory mediator implicated in brain injury. IL-1 expression in the normal CNS is low, but is upregulated rapidly in response to brain injury. In experimental studies, IL-1 and its endogenous, competitive, selective antagonist, IL-1 receptor antagonist (IL-1RA), mediate neurotoxic and neuroprotective outcomes, respectively. Clinical studies support the relationship between inflammation, disease severity and poor prognosis in various neurological and neurosurgical disorders. Recombinant human (rh)IL-1RA shows modest blood–brain barrier penetrance and is safe for clinical use when administered parenterally. Evidence supporting the use of rhIL-1RA and other approaches to targeting IL-1 are discussed in relation to cerebral ischemia, seizures, subarachnoid hemorrhage and traumatic brain injury.

Whole-body moderate hypothermia confers protection from wood smoke-induced acute lung injury in rats: The therapeutic window*

OBJECTIVE

Toxic smoke inhalation causes acute lung injury. We studied the efficacy and therapeutic window of whole-body hypothermia in rats with wood smoke-induced acute lung injury.

DESIGN

Randomized, controlled study.

SETTING

Research laboratory.

SUBJECTS

Anesthetized, paralyzed, and artificially ventilated rats (n = 100) were used.

INTERVENTIONS

Air or wood smoke (30 breaths) was delivered into the lung using a respirator. Immediately after challenge, the rat's colonic temperature was kept a) 37 degrees C (normothermia, NT) for 1 (NT-1-Air and NT-1-Smoke), 2.5 (NT-2.5-Air and NT-2.5-Smoke), or 5 hrs (NT-5-Air and NT-5-Smoke) in six groups; b) 30 degrees C (hypothermia, HT) for 2.5 (HT-2.5-Smoke) or 5 hrs (HT-5-Air and HT-5-Smoke) in three groups; c) 30 degrees C for the first 2.5 hrs followed by 37 degrees C for another 2.5 hrs (HT-NT-5-Smoke) in one group; or d) 37 degrees C for the first 2.5 hrs followed by 30 degrees C for another 2.5 hrs (NT-HT-5-Smoke) in on group.

MEASUREMENTS AND MAIN RESULTS

Various acute lung injury indexes were assessed at 1, 2.5, or 5 hrs after challenge. In the air group, whole-body hypothermia did not affect the level of lung lipid peroxidation and the amount of proteins, total and differential cell counts, and concentrations of tumor necrosis factor-alpha and interleukin-1beta in bronchoalveolar lavage fluid. In the smoke groups, these acute lung injury indexes were increased showing that NT-5-Smoke > NT-2.5-Smoke > NT-1-Smoke. Whole-body hypothermia prevented increases in these acute lung injury indexes in the HT-2.5-Smoke and HT-5-Smoke groups. The efficacy of whole-body hypothermia in the HT-NT-5-Smoke group was superior to that in the NT-HT-5-Smoke group and similar to that in the HT-5-Smoke group. Whole-body hypothermia also alleviated smoke-induced poor gas exchange, pulmonary edema, and pathohistologic injurious signs.

CONCLUSIONS

Whole-body hypothermia confers protection from wood smoke-induced acute lung injury in rats by suppressing oxidant bronchoalveolar damage and pulmonary inflammation. Early and short-period (2 hrs) application of whole-body hypothermia provides favorable therapeutic effects.

Keeping cool in acute liver failure: rationale for the use of mild hypothermia

Encephalopathy, brain edema and intracranial hypertension are neurological complications responsible for substantial morbidity/mortality in patients with acute liver failure (ALF), where, aside from liver transplantation, there is currently a paucity of effective therapies. Mirroring its cerebro-protective effects in other clinical conditions, the induction of mild hypothermia may provide a potential therapeutic approach to the management of ALF. A solid mechanistic rationale for the use of mild hypothermia is provided by clinical and experimental studies showing its beneficial effects in relation to many of the key factors that determine the development of brain edema and intracranial hypertension in ALF, namely the delivery of ammonia to the brain, the disturbances of brain organic osmolytes and brain extracellular amino acids, cerebro-vascular haemodynamics, brain glucose metabolism, inflammation, subclinical seizure activity and alterations of gene expression. Initial uncontrolled clinical studies of mild hypothermia in patients with ALF suggest that it is an effective, feasible and safe approach. Randomized controlled clinical trials are now needed to adequately assess its efficacy, safety, clinical impact on global outcomes and to provide the guidelines for its use in ALF.

The effect of therapeutic hypothermia on the expression of inflammatory response genes following moderate traumatic brain injury in the rat

Traumatic brain injury (TBI) initiates a cascade of cellular and molecular responses including both pro- and anti-inflammatory. Although post-traumatic hypothermia has been shown to improve outcome in various models of brain injury, the underlying mechanisms responsible for these effects have not been clarified. In this study, inflammation cDNA arrays and semi-quantitative RT-PCR were used to detect genes that are differentially regulated after TBI. In addition, the effect of post-traumatic hypothermia on the expression of selective genes was also studied. Rats (n = 6-8 per group) underwent moderate fluid-percussion (F-P) brain injury with and without hypothermic treatment (33 degrees C/3 h). RNA from 3-h or 24-h survival was analyzed for the expression of IL1-beta, IL2, IL6, TGF-beta2, growth-regulated oncogene (GRO), migration inhibitory factor (MIF), and MCP (a transcription factor). The interleukins IL-1beta, IL-2, and IL-6 and TGF-beta and GRO were strongly upregulated early and transiently from 2- to 30-fold over sham at 3 h, with normalization by 24 h. In contrast, the expressions of MIF and MCP were both reduced by TBI compared to sham. Post-traumatic hypothermia had no significant effect on the acute expression of the majority of genes investigated. However, the expression of TGF-beta2 at 24 h was significantly reduced by temperature manipulation. The mechanism by which post-traumatic hypothermia is protective may not involve a general genetic response of the inflammatory genes. However, specific genes, including TGF-beta2, may be altered and effect cell death mechanisms after TBI. Hypothermia differentially regulates certain genes and may target more delayed responses underlying the secondary damage following TBI.

Influence of therapeutic hypothermia on matrix metalloproteinase activity after traumatic brain injury in rats

Recent evidence suggests that matrix metalloproteinases (MMPs) contribute to acute edema and lesion formation following ischemic and traumatic brain injuries (TBI). Experimental and clinical studies have also reported the beneficial effects of posttraumatic hypothermia on histopathological and behavioral outcome. The purpose of this study was to determine whether therapeutic hypothermia would affect the activity of MMPs after TBI. Male Sprague-Dawley rats were traumatized by moderate parasagittal fluid-percussion (F-P) brain injury. Seven groups (n=5/group) of animals were investigated: sham-operated, TBI with normothermia (37 degrees C), and TBI with hypothermia (33 degrees C). Normothermia animals were killed at 4, 24, 72 h and 5 days, and hypothermia animals at 24 or 72 h. Brain temperature was reduced to target temperature 30 mins after trauma and maintained for 4 h. Ipsilateral and contralateral cortical, hippocampal, and thalamic regions were analyzed by gelatin and in situ zymography. In traumatized normothermic animals, TBI significantly (P<0.005) increased MMP-9 levels in ipsilateral (right) cortical and hippocampal regions, compared with contralateral or sham animals, beginning at 4 h and persisting to 5 days. At 1, 3, and 5 days after TBI, significant increases in MMP-2 levels were observed. In contrast to these findings observed with normothermia, posttraumatic hypothermia significantly reduced MMP-9 levels. Hypothermic treatment, however, did not affect the delayed activation of MMP-2. Clarifying the mechanisms underlying the beneficial effects of posttraumatic hypothermia is an active area of research. Posttraumatic hypothermia may attenuate the deleterious consequences of brain trauma by reducing MMP activation acutely.

Mild hypothermia for acute liver failure: a review of mechanisms of action

Brain edema with intracranial hypertension is a major complication in patients with acute liver failure. Current therapies for this complication include a variety of pharmacologic and interventional measures, some of which are frequently associated with adverse effects or contraindications. Even though these measures usually allow the control of intracranial hypertension for a certain period of time, recurrence is common. New therapies are therefore needed. Increasing clinical and experimental evidence suggests that induction of mild hypothermia (32 degrees C-35 degrees C) may be a therapeutic alternative. Similar to traumatic brain injury or brain stroke, induction of mild hypothermia seems highly effective to reduce intracranial pressure in patients with acute liver failure. Several mechanisms by which mild hypothermia may prevent brain edema and intracranial hypertension in this condition have been disclosed and may include beneficial effects on ammonia metabolism, as well as on the disturbances of brain osmolarity, cerebrovascular hemodynamics, brain glucose metabolism, inflammation, and others. Improvement of systemic hemodynamics and amelioration of liver injury may be other benefits of the systemic induction of mild hypothermia, but the impact of potential adverse events, such as infection, should also be taken into account. At a time when mild hypothermia is increasingly used in several specialized centers, performance of a randomized controlled trial seems critical to confirm the benefits of mild hypothermia in acute liver failure and to provide adequate guidelines for its use.

A two-hour window for hypothermic modulation of early events that impact delayed opening of the rat blood-brain barrier after ischemia

Opening of the blood-brain barrier (BBB) and consequent edema are known to intensify 24-72 h after ischemic stroke, and research on potential ameliorative therapies in animal models may lead to improved clinical treatments to prevent brain swelling and the secondary damage it causes. In this study, post-ischemic hypothermia treatment, which is an established neuroprotective strategy, was examined for its ability to prevent delayed BBB opening in a rat model of global ischemia. Anesthetized, normothermic SD rats (340-380 g) underwent 20 min of two-vessel (carotid) occlusion plus hypotension (2VO ischemia, between 0900-1100 h). Marked cortical BBB leakiness, which developed overnight, was indicated at sacrifice 24 h post-2VO by an average six- to eightfold increase above baseline in transfer constant values (K(i) ) for rate of blood to brain diffusion of intravenously delivered [(3)H]sucrose. A post-2VO treatment involving whole body cooling to 31.5 degrees-32.5 degrees C, maintenance for 6 h and rewarming to normothermia, significantly reduced BBB leakiness at 24 h, whether cooling was initiated immediately after reperfusion, or after a 1-h delay, but not after 2-h delay. Immediate hypothermia treatment reduced overall tissue injury at 24 h as evidenced by an assay of mitochondrial succinate dehydrogenase activity, and also reduced brain edema. By contrast, treatment of rats with the anti-inflammatory drugs cyclosporine A or minocycline offered no protection of BBB or mitochondria. It is concluded that hypothermic alteration of critical events during the first 2 h after prolonged ischemia powerfully mitigates the BBB damage and associated events that normally develop 24 h later.

Hypothermia prolongs activation of NF-kappaB and augments generation of inflammatory cytokines

While moderate hypothermia is protective against ischemic cardiac and brain injury, it is associated with much higher mortality in patients with sepsis. We previously showed that in vitro exposure to moderate hypothermia (32 degrees C) delays the induction and prolongs the duration of TNF-alpha and IL-1beta secretion by lipopolysaccharide (LPS)-stimulated human mononuclear phagocytes. In the present study, we extended these observations by showing that moderate hypothermia exerts effects on TNF-alpha and IL-1beta generation in the human THP-1 monocyte cell line that are similar to those that we previously found in primary cultured monocytes; that hypothermia causes comparable changes in cytokine generation stimulated by zymosan, toxic shock syndrome toxin-1, and LPS; and that hypothermia causes similar changes in TNF-alpha and IL-1beta mRNA accumulation. TNF-alpha mRNA half-life, determined after transcriptional arrest with actinomycin D, was not significantly prolonged by lowering incubation temperature from 37 to 32 degrees C, suggesting that hypothermia modifies TNF-alpha gene transcription. This finding was further supported by reporter gene studies showing a threefold increase in activity of the human TNF-alpha promoter at 32 vs. 37 degrees C. Electrophoretic mobility shift assay revealed that hypothermia prolonged NF-kappaBeta activation, identifying a potential role for this transcription factor in mediating the effects of hypothermia on TNF-alpha and IL-1beta production. Delayed reexpression of the inhibitor IkappaBalpha, shown by Northern blotting and immunoblotting, may account in part for the prolonged NF-kappaBeta activation at 32 degrees C. Augmentation of NF-kappaBeta-dependent gene expression during prolonged exposure to hypothermia may be a common mechanism leading to increased lethality in sepsis, late-onset systemic inflammatory response syndrome after accidental hypothermia, and neuroprotection after ischemia.

Mild hypothermia inhibits inflammation after experimental stroke and brain inflammation

BACKGROUND AND PURPOSE

We previously showed that mild hypothermia protects against experimental stroke, even when cooling was delayed by 2 hours. Protection may be due in part to inhibiting inflammation. To clarify, we examined leukocyte infiltration, microglial activation, and adhesion molecule expression in models of stroke and pure brain inflammation.

METHODS

Rats underwent 2-hour middle cerebral artery occlusion (MCAO; n=36) or intravenous injection with 5 mg/kg lipopolysaccharide (LPS; n=22). Temperature was lowered to 33 degrees C for 2 hours or kept at 37 degrees C. In MCAO, cooling was applied intraischemically or on reperfusion (delayed). In the LPS model, cooling began after injection. One and 3 days later, brains were assessed for neutrophils, monocytes/microglia, major histocompatibility complex class II antigen, and intercellular adhesion molecule-1 (ICAM-1).

RESULTS

One day after MCAO, both intraischemic and delayed hypothermia decreased ICAM-1 (51% and 60%, respectively, versus normothermia; P<0.001), monocytes (63% and 57%; P<0.01), and microglia (55% and 53%; P<0.001). Similar decreases were seen at 3 days for ICAM-1 (91% and 93%; P<0.001), monocytes (62% and 54%; P<0.01), and microglia (55% and 53%; P<0.001). In the LPS model, ED-1-positive cells were not observed in the brain, but hypothermia decreased ICAM-1 (26%; P<0.05), OX6 (56%; P<0.01), and microglia (47%; P<0.01) at 1 day.

CONCLUSIONS

Mild hypothermia decreases inflammatory responses in both brain inflammation and stroke, implicating a direct anti-inflammatory effect of cooling. This suggests that hypothermia can attenuate factors contributing to delayed ischemic injury.

Mild hypothermia inhibits nuclear factor-kappaB translocation in experimental stroke

Nuclear factor-kappaB (NFkappaB) is a transcription factor that is activated after cerebral ischemia. NFkappaB activation leads to the expression of many inflammatory genes involved in the pathogenesis of stroke. The authors previously showed that mild hypothermia is protective even when cooling begins 2 h after stroke onset. In the present study, they examined the influence of hypothermia on NFkappaB activation. Rats underwent 2 h of transient middle cerebral artery occlusion. Brains were cooled to 33 degrees C immediately after or 2 h after occlusion, and maintained for 2 h. After normothermic ischemia (brain temperature at 38 degrees C), NFkappaB cytoplasmic expression, nuclear translocation, and binding activity were observed as early as 2 h in the ischemic hemisphere and persisted at 24 h. Hypothermia decreased NFkappaB translocation and binding activity but did not alter overall expression. Hypothermia also affected the levels of NFkappaB regulatory proteins by suppressing phosphorylation of NFkappaB's inhibitory protein (IkappaB-alpha) and IkappaB kinase (IKK-gamma) and decreasing IKK activity, but did not alter overall IKK levels. Hypothermia suppressed the expression of two NFkappaB target genes: inducible nitric oxide synthase and TNF-alpha. These data suggest that the protective effect of hypothermia on cerebral injury is, in part, related to NFkappaB inhibition due to decreased activity of IKK.

Hypothermia attenuates circulatory shock and cerebral ischemia in experimental heatstroke

We tested the hypothesis in a rat model that body cooling suppresses circulatory shock and cerebral ischemia in heatstroke. Animals under urethane anesthesia were exposed to water blanket temperature (Tblanket) of 42 degrees C until mean arterial pressure (MAP) and local cerebral blood flow (CBF) in the hippocampus began to decrease from their peak levels, which was arbitrarily defined as the onset of heatstroke. Control rats were exposed to 26 degrees C. Extracellular concentrations of glutamate, glycerol, lactate, and lactate/pyruvate in the hippocampus were assessed by microdialysis methods. Cooling was accomplished by decreasing Tblanket from 42 degrees C to 16 degrees C. The values of MAP and CBF after the onset of heat stroke in heatstroke rats received no cooling were all significantly lower than those in control rats. However, the neuronal damage score and extracellular levels of ischemia and damage markers in the hippocampus were greater. Cooling immediately after the onset of heatstroke reduced the heatstroke-induced circulatory shock, cerebral ischemia, neuronal damage, and surge of tissue ischemia and damage markers in the hippocampus, and resulted in prolongation of survival time. Delaying the onset of cooling reduced the therapeutic efficiency. The results suggest that body cooling attenuates circulatory shock and cerebral ischemia insults in heatstroke.

Effects of moderate hypothermia on proinflammatory cytokine production in a rat model of caerulein-induced pancreatitis

INTRODUCTION

Proinflammatory cytokines act as mediators of the local and systemic manifestations of acute pancreatitis (AP).

AIMS

To investigate whether moderate hypothermia (MH) (32 degrees C) can reduce the severity of AP by inhibiting cytokine production in a rat model of caerulein-induced pancreatitis.

METHODOLOGY

Rats were divided into three groups: control rats (Group I), AP rats treated with normothermia (38 degrees C) (Group II), and AP rats treated with MH (Group III). AP was induced by intramuscular injection of caerulein and intraperitoneal infusion of lipopolysaccharide. MH was induced 4 hours after the first caerulein injection. Serum interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-6, amylase, and lipase levels were determined 8 hours after the first injection. The pancreas and lung were examined histologically.

RESULTS

MH in comparison with normothermia significantly reduced serum levels of IL-1beta, TNF-alpha, IL-6, amylase, and lipase. Histologically, the MH group showed less vacuolization of the acinar cells and cellular infiltration into the interacinar areas of the pancreas than were shown in the normothermia group, but these effects were not evident in the lung.

CONCLUSION

Our results suggest that MH may be clinically applicable for reducing the severity of AP.

Interleukin-1beta messenger ribonucleic acid and protein levels after fluid-percussion brain injury in rats: importance of injury severity and brain temperature

OBJECTIVE

Posttraumatic temperature manipulations have been reported to significantly influence the inflammatory response to traumatic brain injury (TBI). The purpose of this study was to determine the temporal and regional profiles of messenger ribonucleic acid (mRNA) expression and protein levels for the proinflammatory cytokine interleukin-1beta (IL-1beta), after moderate or severe TBI. The effects of posttraumatic hypothermia (33 degrees C) or hyperthermia (39.5 degrees C) on these consequences of TBI were then determined.

METHODS

Male Sprague-Dawley rats underwent fluid-percussion brain injury. In the first phase of the study, rats were killed 15 minutes or 1, 3, or 24 hours after moderate TBI (1.8-2.2 atmospheres), for reverse transcription-polymerase chain reaction analysis. Other groups of rats were killed 1, 3, 24, or 72 hours after moderate or severe TBI (2.4-2.7 atmospheres), for protein analysis. In the second phase, rats underwent moderate fluid-percussion brain injury, followed immediately by 3 hours of posttraumatic normothermia (37 degrees C), hyperthermia (39.5 degrees C), or hypothermia (33 degrees C), and were then killed, for analyses of protein levels and mRNA expression. Brain samples, including cerebral cortex, hippocampus, thalamus, and cerebellum, were dissected and stored at -80 degrees C until analyzed.

RESULTS

The findings indicated that mRNA levels were increased (P < 0.05) as early as 1 hour after TBI and remained elevated up to 3 hours after moderate TBI. Although both moderate and severe TBI induced increased levels of IL-1beta (P < 0.05), increased protein levels were also noted in remote brain structures after severe TBI. Posttraumatic hypothermia attenuated IL-1beta protein levels, compared with normothermia (P < 0.05), although the levels remained elevated in comparison with sham values. In contrast, hyperthermia had no significant effect on IL-1beta levels, compared with normothermic values. Posttraumatic temperature manipulations had no significant effect on IL-1beta mRNA levels.

CONCLUSION

Injury severity determines the degree of IL-1beta protein level elevation after TBI. The effects of posttraumatic hypothermia on IL-1beta protein levels (an important mediator of neurodegeneration after TBI) may partly explain the established effects of posttraumatic temperature manipulations on inflammatory processes after TBI.

Targeting the host inflammatory response in traumatic spinal cord injury

Both acute and chronic inflammatory processes have been shown to influence outcome in experimental models of spinal cord injury. Although early inflammatory responses may participate in secondary injury processes, more delayed inflammatory events may be reparative. Therapeutic strategies that target these events are currently based on experimental findings that have clarified the cellular and molecular processes involved in the inflammatory response to injury. An increasing body of literature supports the hypothesis that acute inflammatory events are attenuated by therapeutic hypothermia and other anti-inflammatory strategies, whereas immune neuroprotection and axonal regeneration can be achieved by transfer of activated T cells or by treatment with therapeutic vaccines. These data are summarized in the present review.