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

Prolonged hypothermia in rat: a safety study using brain-selective and systemic treatments

Hypothermia is an effective neuroprotectant for cardiac arrest and perinatal ischemic injury. Hypothermia also improves outcome after traumatic brain injury and stroke. Although the ideal treatment parameters (duration, delay, and depth) are not fully delineated, prolonged cooling is usually more effective than shorter periods. There is the concern that extended cooling may be hazardous to brain plasticity and cause damage. In order to evaluate this possibility, we assessed the effects of 3 days of systemic hypothermia (32°C) in rats subjected to a sham stroke surgery. There were no detrimental behavioral effects or signs of brain damage. As even longer cooling may be needed in some patients, we cooled (∼32°C) the right hemisphere of rats for 3 or 21 days. Physiological variables, functional outcome, and measures of cell injury were examined. Focal brain cooling for 21 days modestly decreased heart rate, blood pressure, and core temperature. However, focal hypothermia did not affect subsequent behavior (e.g., spontaneous limb usage), cell morphology (e.g., dendritic arborization, ultrastructure), or cause cell death. In conclusion, prolonged mild hypothermia did not harm the brain of normal animals. Further research is now needed to evaluate whether such treatments affect plasticity after brain injury.

Potential long-term benefits of acute hypothermia after spinal cord injury: assessments with somatosensory-evoked potentials

OBJECTIVE

Neuroprotection by hypothermia has been an important research topic over last two decades. In animal models of spinal cord injury, the primary focus has been assessing the effects of hypothermia on behavioral and histologic outcomes. Although a few studies have investigated electrophysiological changes in descending motor pathways with motor-evoked potentials recorded during cooling, we report here hypothermia induced increased electrical conduction in the ascending spinal cord pathways with somatosensory-evoked potentials in injured rats. In our experiments, these effects lasted long after the acute hypothermia and were accompanied by potential long-term improvements in motor movement.

DESIGN

Laboratory investigation.

SETTING

University medical school.

SUBJECTS

Twenty-one female Lewis rats.

INTERVENTIONS

Hypothermia.

MEASUREMENTS AND MAIN RESULTS

All animals underwent spinal cord contusion with the NYU-Impactor by a 12.5-mm weight drop at thoracic vertebra T8. A group (n = 10) was randomly assigned for a systemic 2-hr hypothermia episode (32 ± 0.5°C) initiated approximately 2.0 hrs postinjury. Eleven rats were controls with postinjury temperature maintained at 37 ± 0.5°C for 2 hrs. The two groups underwent preinjury, weekly postinjury (up to 4 wks) somatosensory-evoked potential recordings and standard motor behavioral tests (BBB). Three randomly selected rats from each group were euthanized for histologic analysis at postinjury day 3 and day 28. Compared with controls, the hypothermia group showed significantly higher postinjury somatosensory-evoked potential amplitudes with longer latencies. The BBB scores were also higher immediately after injury and 4 wks later in the hypothermia group. Importantly, specific changes in the Basso, Beattie, Bresnahan scores in the hypothermia group (not seen in controls) indicated regained functions critical for motor control. Histologic evaluations showed more tissue preservation in the hypothermia group.

CONCLUSIONS

After spinal cord injury, early systemic hypothermia provided significant neuroprotection weeks after injury through improved sensory electrophysiological signals in rats. This was accompanied by higher motor behavioral scores and more spared tissue in acute and postacute periods after injury.

STAT3 signaling after traumatic brain injury

Astrocytes respond to trauma by stimulating inflammatory signaling. In studies of cerebral ischemia and spinal cord injury, astrocytic signaling is mediated by the cytokine receptor glycoprotein 130 (gp130) and Janus kinase (Jak) which phosphorylates the transcription factor signal transducer and activator of transcription-3 (STAT3). To determine if STAT3 is activated after traumatic brain injury (TBI), adult male Sprague-Dawley rats received moderate parasagittal fluid-percussion brain injury or sham surgery, and then the ipsilateral cortex and hippocampus were analyzed at various post-traumatic time periods for up to 7 days. Western blot analyses indicated that STAT3 phosphorylation significantly increased at 30 min and lasted for 24 h post-TBI. A significant increase in gp130 and Jak2 phosphorylation was also observed. Confocal microscopy revealed that STAT3 was localized primarily within astrocytic nuclei. At 6 and 24 h post-TBI, there was also an increased expression of STAT3 pathway-related genes: suppressor of cytokine signaling 3, nitric oxide synthase 2, colony stimulating factor 2 receptor β, oncostatin M, matrix metalloproteinase 3, cyclin-dependent kinase inhibitor 1A, CCAAT/enhancer-binding protein β, interleukin-2 receptor γ, interleukin-4 receptor α, and α-2-macroglobulin. These results clarify some of the signaling pathways operative in astrocytes after TBI and demonstrate that the gp130-Jak2-STAT3 signaling pathway is activated after TBI in astrocytes.

The effect of progesterone dose on gene expression after traumatic brain injury

Microarray-based transcriptional profiling was used to determine the effect of progesterone in the cortical contusion (CCI) model. Gene ontology (GO) analysis then evaluated the effect of dose on relevant biological pathways. Treatment (vehicle, progesterone 10 mg/kg or 20 mg/kg given i.p.) was started 4 h post-injury and administered every 12 h post-injury for up to 72 h, with the last injection 12 hr prior to death for the 24 h and 72 h groups. In the CCI-injured vehicle group compared to non-injured animals, expression of 1,114, 4,229, and 291 distinct genes changed >1.5-fold (p<0.05) at 24 h, 72 h, and 7 days, respectively. At 24 h, the effect of low-dose progesterone on differentially expressed genes was <20% the effect of higher dose compared to vehicle. GO analysis identified a significant effect of low- and high-dose progesterone treatment compared to vehicle on DNA damage response. At 72 h, high-dose progesterone treatment compared to vehicle affected expression of almost twice as many genes as did low-dose progesterone. Both low- and high-dose progesterone resulted in expression of genes regulating inflammatory response and apoptosis. At 7 days, there was only a modest difference in high-dose progesterone compared to vehicle, with only 14 differentially expressed genes. In contrast, low-dose progesterone resulted in 551 differentially expressed genes compared to vehicle. GO analysis identified genes for the low-dose treatment involved in positive regulation of cell proliferation, innate immune response, positive regulation of anti-apoptosis, and blood vessel remodeling.

Targeted temperature management in critical care: a report and recommendations from five professional societies

OBJECTIVE

Representatives of five international critical care societies convened topic specialists and a nonexpert jury to review, assess, and report on studies of targeted temperature management and to provide clinical recommendations.

DATA SOURCES

Questions were allocated to experts who reviewed their areas, made formal presentations, and responded to questions. Jurors also performed independent searches. Sources used for consensus derived exclusively from peer-reviewed reports of human and animal studies.

STUDY SELECTION

Question-specific studies were selected from literature searches; jurors independently determined the relevance of each study included in the synthesis.

CONCLUSIONS AND RECOMMENDATIONS

1) The jury opines that the term "targeted temperature management" replace "therapeutic hypothermia." 2) The jury opines that descriptors (e.g., "mild") be replaced with explicit targeted temperature management profiles. 3) The jury opines that each report of a targeted temperature management trial enumerate the physiologic effects anticipated by the investigators and actually observed and/or measured in subjects in each arm of the trial as a strategy for increasing knowledge of the dose/duration/response characteristics of temperature management. This enumeration should be kept separate from the body of the report, be organized by body systems, and be made without assertions about the impact of any specific effect on the clinical outcome. 4) The jury STRONGLY RECOMMENDS targeted temperature management to a target of 32°C-34°C as the preferred treatment (vs. unstructured temperature management) of out-of-hospital adult cardiac arrest victims with a first registered electrocardiography rhythm of ventricular fibrillation or pulseless ventricular tachycardia and still unconscious after restoration of spontaneous circulation (strong recommendation, moderate quality of evidence). 5) The jury WEAKLY RECOMMENDS the use of targeted temperature management to 33°C-35.5°C (vs. less structured management) in the treatment of term newborns who sustained asphyxia and exhibit acidosis and/or encephalopathy (weak recommendation, moderate quality of evidence).

Effect of therapeutic mild hypothermia on the genomics of the hippocampus after moderate traumatic brain injury in rats

BACKGROUND

Traumatic brain injury (TBI), a major cause of morbidity and mortality, is a serious public health concern.

OBJECTIVE

To evaluate the effect of mild hypothermia on gene expression in the hippocampus and to try to elucidate molecular mechanisms of hypothermic neuroprotection after TBI.

METHODS

Rats were subjected to mild hypothermia (group 1: n = 3, 33 degrees C, 3H) or normothermia (group 2: n = 3; 37 degrees C, 3H) after TBI. Six genome arrays were applied to detect the gene expression profiles of ipsilateral hippocampus. Functional clustering and gene ontology analysis were then carried out. Another 20 rats were randomly assigned to 4 groups (n = 5 per group): group 3, sham-normothermia; group 4, sham-hypothermia; group 5, TBI-normothermia; and group 6, TBI-hypothermia. Real-time fluorescent quantitative reverse-transcription polymerase chain reaction was used to detect specific selected genes.

RESULTS

We found that 133 transcripts in the hypothermia group were statistically different from those in the normothermia group, including 57 transcripts that were upregulated and 76 that were downregulated after TBI (P < .01). Most of these genes were involved in various pathophysiological processes, and some were critical to cell survival. Analysis showed that 9 gene ontology categories were significantly affected by hypothermia, including the most affected categories: synapse organization and biogenesis (upregulated) and regulation of inflammatory response (downregulated). The mRNA expression of Ank3, Cmbp, Nrxn3, Tgm2, and Fcgr3 was regulated by hypothermia, TBI, or a combination of TBI and hypothermia compared with the sham-normothermia group. Their mRNA expression was significantly regulated by hypothermia in TBI groups.

CONCLUSION

Posttraumatic mild hypothermia has a significant effect on the gene expression profiles of the hippocampus, especially those genes belonging to the 9 gene ontology categories. Differential expression of those genes may be involved in the most fundamental molecular mechanisms of cerebral protection by mild hypothermia after TBI.

MIF: a key player in cutaneous biology and wound healing

Owing to its implication in a range of pathological conditions, including asthma, rheumatoid arthritis, atherosclerosis, inflammatory bowel disease and cancer, the pleiotropic cytokine macrophage migration inhibitory factor (MIF) has been the subject of intensive recent investigation. In the field of dermatology, MIF is believed to be a detrimental factor in diseases such as systemic sclerosis, atopic dermatitis, psoriasis, eczema and UV radiation damage. However, its contribution to other aspects of cutaneous biology is currently unclear. Although its expression in intact skin is well characterized, little is known about MIF's role in cutaneous homoeostasis. However, recent data do identify MIF as a key player in the immune privilege of hair follicles. Similarly, although MIF is rapidly released and its local expression significantly induced upon wounding, its primary role in the ensuing repair process remains a source of contention. MIF has been identified as being a key effector of the beneficial effects of estrogen on wound repair, yet studies employing Mif null mice, recombinant MIF, and neutralizing anti-MIF antibodies have failed to provide a consensus as to whether it benefits or inhibits healing. In fact MIF appears to be able to exert both positive and negative effects, with the cell-specific relevancy of MIF in wound healing still unclear. Thus, if MIF and/or its downstream targets are to be therapeutically useful in the context of cutaneous repair, more needs to be done to establish the nature and mechanism of action of MIF and its receptors in healing wounds.

Pharyngeal selective brain cooling is associated with reduced CNS cortical lesion after experimental traumatic brain injury in rats

Therapeutic hypothermia (TH) is still being explored as a therapeutic option after traumatic brain injury (TBI) but clinical data has not supported its efficacy. Experimental approaches were promising, but clinical data did not support its efficacy in the treatment of TBI. A novel approach of pharyngeal selective brain cooling (pSBC), recently introduced by our group, has been accompanied by superior neurofunctional, sensorimotor, and cognitive outcomes. This work is now extended by data on histomorphological and physical outcomes after pSBC in a model of experimental TBI. Male Sprague-Dawley rats were subjected to lateral fluid-percussion (LFP) brain injury, and randomized to the following experimental groups: (1) TBI with pSBC, (2) TBI without pSBC, and (3) sham animals. On day post-injury (DPI) 14, the animals were sacrificed and their brains were harvested for immunohistochemistry using the following antibodies: (1) glial fibrillary acidic protein (GFAP), (2) neurofilament (NF), and (3) synaptophysin (SY). In pSBC animals brain temperature was selectively lowered to 33 ± 0.5°C within 15 min post-injury, and maintained for 180 min after induction, while keeping rectal temperatures at physiological levels. Animals that had undergone pSBC showed a significantly faster recovery of body weight starting on DPI 3, and had gained substantially more weight than TBI-only animals on DPI 14 (p < 0.001), indicating superior physical recovery. Areas of cortical damage were significantly smaller in pSBC animals compared to TBI-only animals (p < 0.01). pSBC was associated with preservation of cortical tissue ipsilateral to the lesion, and superior physical recovery after experimental TBI. These results complement earlier reports in which pSBC was associated with superior neurofunctional and cognitive outcomes using the same experimental model.

The dual role of the neuroinflammatory response after ischemic stroke: modulatory effects of hypothermia

Neuroinflammation is a key element in the ischemic cascade after cerebral ischemia that results in cell damage and death in the subacute phase. However, anti-inflammatory drugs do not improve outcome in clinical settings suggesting that the neuroinflammatory response after an ischemic stroke is not entirely detrimental. This review describes the different key players in neuroinflammation and their possible detrimental and protective effects in stroke. Because of its inhibitory influence on several pathways of the ischemic cascade, hypothermia has been introduced as a promising neuroprotective strategy. This review also discusses the influence of hypothermia on the neuroinflammatory response. We conclude that hypothermia exerts both stimulating and inhibiting effects on different aspects of neuroinflammation and hypothesize that these effects are key to neuroprotection.

Gene expression profiling in brain of mice exposed to the marine neurotoxin ciguatoxin reveals an acute anti-inflammatory, neuroprotective response

BACKGROUND

Ciguatoxins (CTXs) are polyether marine neurotoxins and potent activators of voltage-gated sodium channels. This toxin is carried by multiple reef-fish species and human consumption of ciguatoxins can result in an explosive gastrointestinal/neurologic illness. This study characterizes the global transcriptional response in mouse brain to a symptomatic dose of the highly toxic Pacific ciguatoxin P-CTX-1 and additionally compares this data to transcriptional profiles from liver and whole blood examined previously. Adult male C57/BL6 mice were injected with 0.26 ng/g P-CTX-1 while controls received only vehicle. Animals were sacrificed at 1, 4 and 24 hrs and transcriptional profiling was performed on brain RNA with Agilent whole genome microarrays. RT-PCR was used to independently validate gene expression and the web tool DAVID was used to analyze gene ontology (GO) and molecular pathway enrichment of the gene expression data.

RESULTS

A pronounced 4°C hypothermic response was recorded in these mice, reaching a minimum at 1 hr and lasting for 8 hrs post toxin exposure. Ratio expression data were filtered by intensity, fold change and p-value, with the resulting data used for time course analysis, K-means clustering, ontology classification and KEGG pathway enrichment. Top GO hits for this gene set included acute phase response and mono-oxygenase activity. Molecular pathway analysis showed enrichment for complement/coagulation cascades and metabolism of xenobiotics. Many immediate early genes such as Fos, Jun and Early Growth Response isoforms were down-regulated although others associated with stress such as glucocorticoid responsive genes were up-regulated. Real time PCR confirmation was performed on 22 differentially expressed genes with a correlation of 0.9 (Spearman's Rho, p < 0.0001) with microarray results.

CONCLUSIONS

Many of the genes differentially expressed in this study, in parallel with the hypothermia, figure prominently in protection against neuroinflammation. Pathologic activity of the complement/coagulation cascade has been shown in patients suffering from a chronic form of ciguatera poisoning and is of particular interest in this model. Anti-inflammatory processes were at work not only in the brain but were also seen in whole blood and liver of these animals, creating a systemic anti-inflammatory environment to protect against the initial cellular damage caused by the toxin.

The evidence for hypothermia as a neuroprotectant in traumatic brain injury

This article reviews published experimental and clinical evidence for the benefits of modest hypothermia in the treatment of traumatic brain injury (TBI). Therapeutic hypothermia has been reported to improve outcome in several animal models of CNS injury and has been successfully translated to specific patient populations. A PubMed search for hypothermia and TBI was conducted, and important papers were selected for review. The research summarized was conducted at major academic institutions throughout the world. Experimental studies have emphasized that hypothermia can affect multiple pathophysiological mechanisms thought to participate in the detrimental consequences of TBI. Published data from several relevant clinical trials on the use of hypothermia in severely injured TBI patients are also reviewed. The consequences of mild to moderate levels of hypothermia introduced by different strategies to the head-injured patient for variable periods of time are discussed. Both experimental and clinical data support the beneficial effects of modest hypothermia following TBI in specific patient populations. Following on such single-institution studies, positive findings from multicenter TBI trials will be required before this experimental treatment can be considered standard of care.

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.

Effect of post-traumatic mild hypothermia on hippocampal cell death after traumatic brain injury in rats

In this investigation, we evaluated the effect of post-traumatic mild hypothermia on cell death in the hippocampus after fluid percussion traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were randomly divided into three groups (n = 40/group): TBI with hypothermia treatment (32 degrees C), TBI with normothermia (37 degrees C), and sham injury. The TBI model was induced by a fluid percussion TBI device. Mild hypothermia (32 degrees C) was achieved by partial immersion in a water bath (0 degrees C) under general anesthesia for 4h. All rats were killed at 24 or 72h after TBI. The ipsilateral hippocampal CA1 in all rats were analyzed by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL), and 4',6-diamidino-2-phenylindole (DAPI) staining for determining cell death. Caspase-3 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. At 24h, based on TUNEL and DAPI results, the cell death index was 28.80 +/- 2.60% and 32.10 +/- 1.40% in the normothermia TBI group, while reaching only 14.30 +/- 2.70% and 18.40 +/- 2.10% in the hypothermic TBI group (p < 0.01). Based on RT-PCR and Western blotting results, the expression of caspase-3 was 210.20 +/- 5.30% and 170.30 +/- 4.80% in the normothermic TBI group, while reaching only 165.10 +/- 3.70% and 130.60 +/- 4.10% in the hypothermic TBI group (p < 0.05). At 72h, based on TUNEL and DAPI results, the cell death index was 20.80 +/- 2.50% and 25.50 +/- 1.80% in the normothermic TBI group, while reaching only 10.20 +/- 2.60% and 15.50 +/- 2.10% in the hypothermic TBI group (p < 0.01). Based on RT-PCR and Western blotting results, the expression of caspase-3 was 186.20 +/- 6.20% and 142.30 +/- 5.10% in the normothermic TBI group, versus only 152.10 +/- 3.60% and 120.60 +/- 3.90% in the hypothermic TBI group (p < 0.05). Based on our findings, we conclude that post-traumatic hypothermia significantly attenuates cell death within the hippocampus following fluid percussion injury. Taken together with other studies, these observations support the premise that post-traumatic mild hypothermia can provide cerebral protection for patients with TBI.

Effect of 35 degrees C hypothermia on intracranial pressure and clinical outcome in patients with severe traumatic brain injury

BACKGROUND

From 1994, we have used therapeutic hypothermia in patients with severe traumatic brain injury (Glasgow Coma Scale scores of 5 or less). In 2000, we altered the target temperature to 35 degrees C from the former 33 degrees C, as our findings suggested that cooling to 35 degrees C is sufficient to control intracranial hypertension, and that hypothermia below 35 degrees C may predispose patients to persistent cumulative oxygen debt. We attempted to clarify whether 35 degrees C hypothermia has the same effect as 33 degrees C hypothermia in reducing intracranial hypertension and whether it is associated with fewer complications and improved outcomes.

METHODS

We compared intracranial pressure (ICP) and biochemical parameters in the 30 patients treated with 35 degrees C hypothermia (January 2000 to June 2005) with those in the 31 patients treated with 33 degrees C hypothermia (July 1994 to December 1999).

RESULTS

Patient characteristics were similar in the two groups. The mean temperature during hypothermia was 35.1 +/- 0.7 degrees C in the 35 degrees C hypothermia group and 33.4 +/- 0.8 degrees C in the 33 degrees C hypothermia group. Mean ICP was controlled under 20 mm Hg during hypothermia in both the 35 degrees C hypothermia and 33 degrees C hypothermia groups. The incidence of intracranial hypertension and low cerebral perfusion pressure did not differ between the two groups. The 35 degrees C hypothermic patients exhibited a significant improvement in the decline of serum potassium concentrations during hypothermia and in the increment of C-reactive protein after rewarming. The mortality rate and the incidence of systemic complications tended to be lower in the 35 degrees C group.

CONCLUSIONS

Cooling patients to 35 degrees C is safe and the ICP reduction effects of 35 degrees C hypothermia are similar to those of 33 degrees C hypothermia.

The genomic profile of the cerebral cortex after closed head injury in mice: effects of minocycline

Microarray analysis was used to delineate gene expression patterns and profile changes following traumatic brain injury (TBI) in mice. A parallel microarray analysis was carried out in mice with TBI that were subsequently treated with minocycline, a drug proposed as a neuroprotectant in other neurological disorders. The aim of this comparison was to identify pathways that may be involved in secondary injury processes following TBI and potential specific pathways that could be targeted with second generation therapeutics for the treatment of neurotrauma patients. Gene expression profiles were measured with the compugen long oligo chip and real-time PCR was used to validate microarray findings. A pilot study of effect of minocycline on gene expression following TBI was also carried out. Gene ontology comparison analysis of sham TBI and minocycline treated brains revealed biological pathways with more genes differentially expressed than predicted by chance. Among 495 gene ontology categories, the significantly different gene ontology groups included chemokines, genes involved in cell surface receptor-linked signal transduction and pro-inflammatory cytokines. Expression levels of some key genes were validated by real-time quantitative PCR. This study confirms that multiple regulatory pathways are affected following brain injury and demonstrates for the first time that specific genes and molecular networks are affected by minocycline following brain injury.

TGF beta2-induced changes in LRP-1/T beta R-V and the impact on lysosomal A beta uptake and neurotoxicity

Numerous studies suggest a central role for the low-density lipoprotein receptor-related protein/transforming growth factor beta receptor V in Alzheimer's Disease. We continue our investigation of a ligand for this receptor, transforming growth factor beta2, which is also implicated in Alzheimer Disease pathogenesis, but whose mechanism(s) remain elusive. Confocal imaging reveals that transforming growth factor beta2 rapidly targets amyloid beta peptide to the lysosomal compartment in cortical neurons and induces cell death. Low-density lipoprotein receptor-related protein/transforming growth factor beta receptor V is known as an endocytic receptor, delivering proteins to the lysosomal compartment for degradation. Transforming growth factor beta2 may alter this pathway resulting in increased uptake, intracellular accumulation and toxicity of amyloid beta peptide. RT-PCR and Western blot analysis of transforming growth factor beta2-treated cells demonstrate that transforming growth factor beta2 modestly increases the mRNA and protein levels of low-density lipoprotein receptor-related protein/transforming growth factor beta receptor V as well as increases the uptake activity. Furthermore, transforming growth factor beta2 alters the morphology and numbers of lysosomes in neurons. Lucifer Yellow and lysosomal hydrolase analysis show that transforming growth factor beta2 makes lysosomal membranes unstable and leaky and this effect is exacerbated with the addition of amyloid beta protein. Our data support a key role for low-density lipoprotein receptor-related protein/transforming growth factor beta receptor V in mediating transforming growth factor beta2 enhancement of amyloid beta peptide uptake and neurotoxicity.

Biomarkers of primary and evolving damage in traumatic and ischemic brain injury: diagnosis, prognosis, probing mechanisms, and therapeutic decision making

PURPOSE OF REVIEW

Emerging data suggest that biomarkers of brain injury have potential utility as diagnostic, prognostic, and therapeutic adjuncts in the setting of traumatic and ischemic brain injury. Two approaches are being used, namely, assessing markers of structural damage and quantifying mediators of the cellular, biochemical, or molecular cascades in secondary injury or repair. Novel proteomic, multiplex, and lipidomic methods are also being applied.

RECENT FINDINGS

Biochemical markers of neuronal, glial, and axonal damage such as neuron-specific enolase, S100B, and myelin basic protein, respectively, are readily detectable in biological samples such as serum or cerebrospinal fluid and are being studied in patients with ischemic and traumatic brain injury. In addition, a number of studies have demonstrated that novel tools to assess simultaneously multiple biomarkers can provide unique insight such as details on specific molecular participants in cell death cascades, inflammation, or oxidative stress.

SUMMARY

Multifaceted cellular, biochemical, and molecular monitoring of proteins and lipids is logical as an adjunct to guiding therapies and improving outcomes in traumatic and ischemic brain injury and we appear to be on the verge of a breakthrough with the use of these markers as diagnostic, prognostic, and monitoring adjuncts, in neurointensive care.

Housekeeping while brain's storming Validation of normalizing factors for gene expression studies in a murine model of traumatic brain injury

BACKGROUND

Traumatic brain injury models are widely studied, especially through gene expression, either to further understand implied biological mechanisms or to assess the efficiency of potential therapies. A large number of biological pathways are affected in brain trauma models, whose elucidation might greatly benefit from transcriptomic studies. However the suitability of reference genes needed for quantitative RT-PCR experiments is missing for these models.

RESULTS

We have compared five potential reference genes as well as total cDNA level monitored using Oligreen reagent in order to determine the best normalizing factors for quantitative RT-PCR expression studies in the early phase (0-48 h post-trauma (PT)) of a murine model of diffuse brain injury. The levels of 18S rRNA, and of transcripts of beta-actin, glyceraldehyde-3P-dehydrogenase (GAPDH), beta-microtubulin and S100beta were determined in the injured brain region of traumatized mice sacrificed at 30 min, 3 h, 6 h, 12 h, 24 h and 48 h post-trauma. The stability of the reference genes candidates and of total cDNA was evaluated by three different methods, leading to the following rankings as normalization factors, from the most suitable to the less: by using geNorm VBA applet, we obtained the following sequence: cDNA(Oligreen); GAPDH > 18S rRNA > S100beta > beta-microtubulin > beta-actin; by using NormFinder Excel Spreadsheet, we obtained the following sequence: GAPDH > cDNA(Oligreen) > S100beta > 18S rRNA > beta-actin > beta-microtubulin; by using a Confidence-Interval calculation, we obtained the following sequence: cDNA(Oligreen) > 18S rRNA; GAPDH > S100beta > beta-microtubulin > beta-actin.

CONCLUSION

This work suggests that Oligreen cDNA measurements, 18S rRNA and GAPDH or a combination of them may be used to efficiently normalize qRT-PCR gene expression in mouse brain trauma injury, and that beta-actin and beta-microtubulin should be avoided. The potential of total cDNA as measured by Oligreen as a first-intention normalizing factor with a broad field of applications is highlighted. Pros and cons of the three methods of normalization factors selection are discussed. A generic time- and cost-effective procedure for normalization factor validation is proposed.

Incensole acetate: a novel neuroprotective agent isolated from Boswellia carterii

Boswellia resin has been used as a major anti-inflammatory agent and for the healing of wounds for centuries. Incensole acetate (IA), isolated from this resin, was shown to inhibit the activation of nuclear factor-kappaB, a key transcription factor in the inflammatory response. We now show that IA inhibits the production of inflammatory mediators in an in vitro model system of C6 glioma and human peripheral monocytes. Given the involvement of postinjury inflammation in the pathophysiology and outcome of traumatic brain injury, we examined the effect of IA on the inflammatory process and on the recovery of neurobehavioral and cognitive functions in a mouse model of closed head injury (CHI). In the brains of post-CHI mice, IA reduced glial activation, inhibited the expression of interleukin-1beta, and tumor necrosis factor-alpha mRNAs, and induced cell death in macrophages at the area of trauma. A mild hypothermic effect was also noted. Subsequently, IA inhibited hippocampal neurodegeneration and exerted a beneficial effect on functional outcome after CHI, indicated by reduced neurological severity scores and improved cognitive ability in an object recognition test. This study attributes the anti-inflammatory activity of Boswellia resin to IA and related cembranoid diterpenes and suggests that they may serve as novel neuroprotective agents.

Multiplex assessment of cytokine and chemokine levels in cerebrospinal fluid following severe pediatric traumatic brain injury: effects of moderate hypothermia

This study performed a comprehensive analysis of cerebrospinal fluid (CSF) cytokine levels after severe traumatic brain injury (TBI) in children using a multiplex bead array assay and to evaluate the effects of moderate hypothermia on cytokine levels. To this end, samples were collected during two prospective randomized controlled trials of therapeutic moderate hypothermia in pediatric TBI. Thirty-six children with severe TBI (Glasgow Coma Scale [GCS] score of <or=8) and 10 children with negative diagnostic lumbar punctures. All children with TBI had continuous monitoring of intracranial pressure and CSF drainage via an intraventricular catheter. Moderate hypothermia (32-33 degrees C) was maintained for 48 h in 17 patients, and they were slowly re-warmed at 48-72 h. A multiplex bead array assay was used to analyze serial CSF samples (<18 h, 24 +/- 6 h, 48 +/- 6 h, and 72 +/- 6 h) for 21 pro-and anti-inflammatory cytokines and chemokines. Interleukin (IL)-8 and transforming growth factor beta were measured by enzyme-linked immunosorbant assay (ELISA). There was a strong correlation (Spearman correlation coefficient = 0.92, p < 0.001) between multiplex assay and ELISA for IL-8. Pro-inflammatory IL-1beta, -6 and -12p70, anti-inflammatory IL-10 and chemokines IL-8 and MIP-1alpha were increased after TBI compared to controls, p < 0.05; however, there was no association between cytokines and age, gender, initial GCS, or outcome. Hypothermia did not attenuate the increases in CSF cytokine levels after TBI versus normothermia. This investigation confirmed that the multiplex bead array assay is a useful method to measure CSF cytokine levels. Severe TBI in infants and children induces increases in pro- and anti-inflammatory cytokines and chemokines. It is the first clinical report of increased levels of MIP-1alpha after TBI in any patient population and the most comprehensive assessment of cytokines after TBI to date. Moderate therapeutic hypothermia did not attenuate the increase in CSF cytokine levels in children after TBI.

Effects of therapeutic mild hypothermia on patients with severe traumatic brain injury after craniotomy

PURPOSE

We investigated the effects of therapeutic mild hypothermia on patients with severe traumatic brain injury after craniotomy (TBI).

METHODS

Eighty patients with severe TBI after unilateral craniotomy were randomized into a therapeutic hypothermia group with the brain temperature maintained at 33 degrees C to 35 degrees C for 4 days, and a normothermia control group in the intensive care unit. Vital signs, intracranial pressure, serum superoxide dismutase level, Glasgow Outcome Scale scores, and complications were prospectively analyzed.

RESULTS

The mean intracranial pressure values of the therapeutic hypothermia group at 24, 48, and 72 hours after injury were much lower than those of the control group (23.49 +/- 2.38, 24.68 +/- 1.71, and 22.51 +/- 2.44 vs 25.87 +/- 2.18, 25.90 +/- 1.86, and 24.57 +/- 3.95 mm Hg; P = .000, .000, and .003, respectively). The mean serum superoxide dismutase levels of the therapeutic hypothermia group at days 3 and 7 were much higher than those of the control group at the same time point (533.0 +/- 103.4 and 600.5 +/- 82.9 vs 458.7 +/- 68.1 and 497.0 +/- 57.3 mug/L, respectively; P = .000). The percentage of favorable neurologic outcome 1 year after injury was 70.0% and 47.5%, respectively (P = .041). Complications, including pulmonary infections (57.5% in the therapeutic hypothermia group vs 32.5% in the control group; P = .025) were managed without severe sequelae.

CONCLUSIONS

Therapeutic mild hypothermia provides a promising way in the intensive care unit for patients with severe TBI after craniotomy.

Hypothermia treatment potentiates ERK1/2 activation after traumatic brain injury

Traumatic brain injury (TBI) results in significant hippocampal pathology and hippocampal-dependent memory loss, both of which are alleviated by hypothermia treatment. To elucidate the molecular mechanisms regulated by hypothermia after TBI, rats underwent moderate parasagittal fluid-percussion brain injury. Brain temperature was maintained at normothermic or hypothermic temperatures for 30 min prior and up to 4 h after TBI. The ipsilateral hippocampus was assayed with Western blotting. We found that hypothermia potentiated extracellular signal-regulated kinase 1/2 (ERK1/2) activation and its downstream effectors, p90 ribosomal S6 kinase (p90RSK) and the transcription factor cAMP response element-binding protein. Phosphorylation of another p90RSK substrate, Bad, also increased with hypothermia after TBI. ERK1/2 regulates mRNA translation through phosphorylation of mitogen-activated protein kinase-interacting kinase 1 (Mnk1) and the translation factor eukaryotic initiation factor 4E (eIF4E). Hypothermia also potentiated the phosphorylation of both Mnk1 and eIF4E. Augmentation of ERK1/2 activation and its downstream signalling components may be one molecular mechanism that hypothermia treatment elicits to improve functional outcome after TBI.

Effect on gene expression of therapeutic hypothermia in cerebral ischemia

Therapeutic hypothermia has gained considerable interest, given that it appears to improve neurological outcomes in patients who have suffered cardiac arrest. In spite of its remarkable beneficial effect, the mechanism of protection by brain cooling is still unclear. Hypothermia is known to alter gene expression; thus, gene profiling may help to identify relevant mechanisms of neuroprotection. Recent studies have demonstrated that brain ischemia-induced gene expression is modulated by hypothermia, but the mechanism of hypothermic gene regulation is quite diverse. Hypothermia can alter transcription factors, leading to changes in gene and protein expression. Enhanced or reduced mRNA stability can also influence gene transcription. This review will summarize reports of altered gene expression following hypothermic treatment in brain ischemia.

Lovastatin improves histological and functional outcomes and reduces inflammation after experimental traumatic brain injury

Traumatic brain injury (TBI) triggers a complex sequence of inflammatory responses that contribute to secondary injury. Statins have demonstrated neuroprotective effects against brain injury, but the underlying mechanisms remain unclear. This study evaluated the effects of lovastatin on a rat model of controlled cortical impact (CCI) injury. Our two hypotheses were that pre-administration of lovastatin would reduce functional deficits and extent of anatomical brain damage and that lovastatin would attenuate levels of pro-inflammatory cytokines. Rats were injected with lovastatin (4 mg/kg) or vehicle for 5 days and subjected to CCI. Neurological status was evaluated using rotarod and adhesive removal tests. Contusion volume and neuronal degeneration were examined using cresyl violet and FluoroJade B (FJB) histochemistry. Levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA and protein were assessed by real-time quantitative reverse transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. Lovastatin significantly improved performance on both the rotarod and adhesive removal tests before post-injury day 7. Lovastatin also significantly reduced contusion volume (20%) and number of FJB-positive degenerating neurons (35%) at 4 days. These changes were associated with a significant decrease in levels of TNF-alpha and IL-1beta mRNA and protein at the contusion site at 6 h and 4 days, respectively. Our results show that pre-administration of lovastatin improved functional outcomes and reduced extent of brain damage, with a concomitant decrease in tissue levels of TNF-alpha and IL-1beta mRNA and protein. These findings suggest that lovastatin's protective mechanisms may be partly attributed to a dampening of the inflammatory response.

Trauma-associated inflammatory response impairs embryonic stem cell survival and integration after implantation into injured rat brain

Pluripotent embryonic stem cells were shown to survive and differentiate into mature neuronal cells after implantation in experimental models of Parkinson disease and cerebral ischemia. Embryonic stem cell transplantation has also been proposed as a potential therapy for cerebral trauma, characteristic of massive loss of multiple cell types due to primary insult and secondary sequelae. Green fluorescent protein (GFP)-transfected murine embryonic stem cells were implanted into the ipsi or contralateral cortex of male Sprague-Dawley rats 72 h after fluid-percussion injury. Animals were sacrificed at day 5 or week 7 postimplantation. Brain sections were examined using conventional and fluorescent double-labelling immunohistochemistry. Five days after implantation, clusters of GFP-positive cells undergoing partial differentiation along neuronal pathway, were detected at the implantation site. However, after 7 weeks, only a few GFP-positive cells were found, indicating an extensive loss of stem cells during this time period. For the first time, we proved the observed cell loss to be mediated via phagocytosis of implanted cells by activated macrophages. Cerebral trauma, induced 3 days prior to implantation, has activated the inflammatory potential of otherwise immunologically privileged tissue. Subsequent cell implantation was accompanied by reactive astrogliosis, activation of microglia, as well as a massive invasion of macrophages into transplantation sites even if the grafts were placed into contralateral healthy hemispheres, remote from the traumatic lesion. Our results demonstrate a significant post-traumatic inflammatory response, which impairs survival and integration of implanted stem cells and has generally not been taken into account in designs of previous transplantation studies.

Electromagnetic controlled cortical impact device for precise, graded experimental traumatic brain injury

Genetically modified mice represent useful tools for traumatic brain injury (TBI) research and attractive preclinical models for the development of novel therapeutics. Experimental methods that minimize the number of mice needed may increase the pace of discovery. With this in mind, we developed and characterized a prototype electromagnetic (EM) controlled cortical impact device along with refined surgical and behavioral testing techniques. By varying the depth of impact between 1.0 and 3.0 mm, we found that the EM device was capable of producing a broad range of injury severities. Histologically, 2.0-mm impact depth injuries produced by the EM device were similar to 1.0-mm impact depth injuries produced by a commercially available pneumatic device. Behaviorally, 2.0-, 2.5-, and 3.0-mm impacts impaired hidden platform and probe trial water maze performance, whereas 1.5-mm impacts did not. Rotorod and visible platform water maze deficits were also found following 2.5- and 3.0-mm impacts. No impairment of conditioned fear performance was detected. No differences were found between sexes of mice. Inter-operator reliability was very good. Behaviorally, we found that we could statistically distinguish between injury depths differing by 0.5 mm using 12 mice per group and between injury depths differing by 1.0 mm with 7-8 mice per group. Thus, the EM impactor and refined surgical and behavioral testing techniques may offer a reliable and convenient framework for preclinical TBI research involving mice.

Subcellular Stress Response after Traumatic Brain Injury

Traumatic brain injury (TBI) initiates a complex genetic response that may include the expression of organelle specific stress genes. We investigated the effects of brain trauma on the expression of a number of stress genes by in situ hybridization and Western blot analysis including the endoplasmic reticulum (ER) stress gene grp78, ER protein processing enzymes calnexin and protein disulphide isomerase (PDI), the mitochondrial stress gene hsp60, and the cytoplasmic stress gene hsp70. Male Sprague-Dawley rats were subjected either to sham-surgery or moderate (1.8-2.2 atm) parasagittal fluid-percussion (F-P) brain injury followed by 30 min of either normoxic or hypoxic (30-40 mm Hg) gas levels. Expression of grp78 was increased in the ipsilateral cerebral cortex and dentate gyrus beginning 4 h after trauma plus hypoxia. Similarly, mRNA encoding the mitochondrial hsp60 was induced in the ipsilateral outer cortical layers at 4-24 h after TBI plus hypoxia. Calnexin and PDI mRNAs were not significantly altered following TBI with or without secondary hypoxia. In contrast, mRNA of the cytoplasmic hsp70 was strongly induced at 4 h after brain injury in multiple brain regions within the injured hemisphere, and this expression was greatly enhanced by secondary hypoxia. Because subcellular stress gene expression may reflect where unfolded or damaged proteins are abundant, these findings suggest that abnormal proteins are localized mainly in the cytoplasm, and to a lesser degree in the ER lumen and mitochondria after brain trauma. Thus, distinct parts of the cellular machinery respond to traumatic and metabolic stresses in specific ways.

Traumatic injury to the immature brain: inflammation, oxidative injury, and iron-mediated damage as potential therapeutic targets

Traumatic brain injury (TBI) is the leading cause of morbidity and mortality among children and both clinical and experimental data reveal that the immature brain is unique in its response and vulnerability to TBI compared to the adult brain. Current therapies for pediatric TBI focus on physiologic derangements and are based primarily on adult data. However, it is now evident that secondary biochemical perturbations play an important role in the pathobiology of pediatric TBI and may provide specific therapeutic targets for the treatment of the head-injured child. In this review, we discuss three specific components of the secondary pathogenesis of pediatric TBI-- inflammation, oxidative injury, and iron-induced damage-- and potential therapeutic strategies associated with each. The inflammatory response in the immature brain is more robust than in the adult and characterized by greater disruption of the blood-brain barrier and elaboration of cytokines. The immature brain also has a muted response to oxidative stress compared to the adult due to inadequate expression of certain antioxidant molecules. In addition, the developing brain is less able to detoxify free iron after TBI-induced hemorrhage and cell death. These processes thus provide potential therapeutic targets that may be tailored to pediatric TBI, including anti-inflammatory agents such as minocycline, antioxidants such as glutathione peroxidase, and the iron chelator deferoxamine.

Allopregnanolone, a Progesterone Metabolite, Is More Effective Than Progesterone in Reducing Cortical Infarct Volume After Transient Middle Cerebral Artery Occlusion

STUDY OBJECTIVE

We compare the effects of postinjury administration of allopregnanolone, a metabolite of progesterone, to progesterone in an animal model of transient middle cerebral artery occlusion.

METHODS

Focal cerebral ischemia was induced in age-matched, adult, male, Sprague-Dawley rats by using an intraluminal filament and suture method to occlude the right middle cerebral artery. After 120 minutes of middle cerebral artery occlusion, the occluding filament was withdrawn to allow reperfusion. Laser-Doppler flowmetry was used to monitor cerebral blood flow for the entire 2-hour period of occlusion and for 5 minutes after reperfusion. Animals subjected to middle cerebral artery occlusion received injections of allopregnanolone (8 mg/kg, n=6), progesterone (8 mg/kg, n=6) and vehicle (2-hydroxypropyl-beta-cyclodextrin, n=7) at 2 hours (intraperitoneally 5 minutes before reperfusion) and 6 hours (subcutaneously) postocclusion. Brains were removed at 72 hours post-middle cerebral artery occlusion, sectioned into coronal slices, and stained with 2,3,5-triphenyltetrazolium chloride (TTC). In a blinded analysis, infarct volume was calculated by using computer-aided morphometry to measure brain areas not stained with TTC.

RESULTS

After progesterone or allopregnanolone treatment, stained sections revealed a significant reduction in cortical, caudate-putamen, and hemispheric infarct volumes (percentage of contralateral structure) compared with vehicle-injected controls. Cortical infarction (percentage of contralateral cortex) was 37.47%+/-10.57% (vehicle), 25.49%+/-7.38% (progesterone; P<.05 from vehicle), and 11.40%+/-7.09% (allopregnanolone; P<.05 from vehicle; P<.05 from progesterone). Caudate-putamen infarction (percentage of contralateral caudate-putamen) was 78.02%+/-22.81% (vehicle), 48.41%+/-22.44% (progesterone; P<.05 from vehicle), and 50.44%+/-10.90% (allopregnanolone; P<.05 from vehicle). Total hemispheric infarction (percentage of contralateral hemisphere) was 24.37%+/-6.69% (vehicle), 15.95%+/-3.59% (progesterone; P<.05 from vehicle), and 11.54%+/-3.71% (allopregnanolone; P<.05 from vehicle). No significant differences in cerebral blood flow between groups and time points during ischemia and early reperfusion were observed, suggesting that the relative ischemic insult was equivalent among all groups.

CONCLUSION

Although progesterone and allopregnanolone are effective in reducing infarct pathology, allopregnanolone is more potent than progesterone in attenuating cortical damage. Our results suggest that both neurosteroids should be examined for safety and efficacy in a clinical trial for ischemic stroke.