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

Pharmacokinetics during therapeutic hypothermia in neonates: from pathophysiology to translational knowledge and physiologically-based pharmacokinetic (PBPK) modeling

INTRODUCTION

Perinatal asphyxia (PA) still causes significant morbidity and mortality. Therapeutic hypothermia (TH) is the only effective therapy for neonates with moderate to severe hypoxic-ischemic encephalopathy after PA. These neonates need additional pharmacotherapy, and both PA and TH may impact physiology and, consequently, pharmacokinetics (PK) and pharmacodynamics (PD).

AREAS COVERED

This review provides an overview of the available knowledge in PubMed (until November 2022) on the pathophysiology of neonates with PA/TH. In vivo pig models for this setting enable distinguishing the effect of PA versus TH on PK and translating this effect to human neonates. Available asphyxia pig models and methodological considerations are described. A summary of human neonatal PK of supportive pharmacotherapy to improve neurodevelopmental outcomes is provided.

EXPERT OPINION

To support drug development for this population, knowledge from clinical observations (PK data, real-world data on physiology), preclinical (in vitro and in vivo (minipig)) data, and molecular and cellular biology insights can be integrated into a predictive physiologically-based PK (PBPK) framework, as illustrated by the I-PREDICT project (Innovative physiology-based pharmacokinetic model to predict drug exposure in neonates undergoing cooling therapy). Current knowledge, challenges, and expert opinion on the future directions of this research topic are provided.

HSC70 as a sensor of low temperature: role in cold-triggered autoinflammatory disorders

Familial cold autoinflammatory syndrome (FCAS) is a subset of heritable autoinflammatory disorders wherein inflammatory symptoms aggravate upon exposure of the individual to subnormal temperature. In the past two decades, several mutations in various genes such as NLRP3, NLRP12, PLCG2 and NLRC4 have been identified that cause cold-triggered inflammation. However, our understanding of the mechanisms by which cells perceive subnormal temperature, and what keeps the inflammation under check until exposure to low temperature, is very limited. We hypothesise that recognition of FCAS-associated mutants as misfolded polypeptides by temperature-sensitive HSC70 (HSPA8) chaperone determines the FCAS phenotype. At 37 °C, HSC70 would interact with the mutant proteins, keeping them almost inactive, and loss of interaction at low temperature due to a conformational change in HSC70 would lead to their activation. The proposed mechanism of low temperature sensing in the context of FCAS may have wider implications for HSC70 as a cold temperature sensor in various pathological conditions where symptoms get aggravated upon exposure to low temperature.

Effects of peripheral administration of lipopolysaccharide on chronic sickness responses in TRPM8-deficient mice

Transient receptor potential melastatin 8 (TRPM8) is a cold-sensing thermoreceptor cation channel; however, its functional role in endotoxin-induced neuroinflammation remains unclear. In the present study, we investigated chronic sickness responses in TRPM8 knockout (KO) mice during lipopolysaccharide (LPS)-induced sepsis. The intraperitoneal administration of 5 mg/kg LPS generated longer-lasting hypothermia in TRPM8 KO mice than in wild-type (WT) mice. TRPM8 KO mice also exhibited longer-lasting declines in locomotor activity, body weight, and food and water intakes than WT mice upon LPS administration. In addition, LPS-induced decreases in the numbers of leucocytes and lymphocytes that persisted for a longer time in TRPM8 KO mice than in WT mice. The present results indicate TRPM8 attenuated chronic sickness responses in endotoxin-induced sepsis.

The Influence of Temperature on the Antiviral Response of mIgM+ B Lymphocytes Against Hirame Novirhabdovirus in Flounder (Paralichthys olivaceus)

Hirame novirhabdovirus (HIRRV) is an ongoing threat to the aquaculture industry. The water temperature for the onset of HIRRV is below 15°C, the peak is about 10°C, but no mortality is observed over 20°C. Previous studies found the positive signal of matrix protein of HIRRV (HIRRV-M) was detected in the peripheral blood leukocytes of viral-infected flounder. Flow cytometry and indirect immunofluorescence assay showed that HIRRV-M was detected in mIgM⁺ B lymphocytes in viral-infected flounder maintained at 10°C and 20°C, and 22% mIgM⁺ B lymphocytes are infected at 10°C while 13% are infected at 20°C, indicating that HIRRV could invade into mIgM⁺ B lymphocytes. Absolute quantitative RT-PCR showed that the viral copies in mIgM⁺ B lymphocytes were significantly increased at 24 h post infection (hpi) both at 10°C and 20°C, but the viral copies in 10°C infection group were significantly higher than that in 20°C infection group at 72 hpi and 96 hpi. Furthermore, the B lymphocytes were sorted from HIRRV-infected flounder maintained at 10°C and 20°C for RNA-seq. The results showed that the differentially expression genes in mIgM⁺ B lymphocyte of healthy flounder at 10°C and 20°C were mainly enriched in metabolic pathways. Lipid metabolism and Amino acid metabolism were enhanced at 10°C, while Glucose metabolism was enhanced at 20°C. In contrast, HIRRV infection at 10°C induced the up-regulation of the Complement and coagulation cascades, FcγR-mediated phagocytosis, Platelets activation, Leukocyte transendothelial migration and Natural killer cell mediated cytotoxicity pathways at 72 hpi. HIRRV infection at 20°C induced the up-regulation of the Antigen processing and presentation pathway at 72 hpi. Subsequently, the temporal expression patterns of 16 genes involved in Antigen processing and presentation pathway were investigated by qRT-PCR, and results showed that the pathway was significantly activated by HIRRV infection at 20°C but inhibited at 10°C. In conclusion, HIRRV could invade into mIgM⁺ B lymphocytes and elicit differential immune response under 10°C and 20°C, which provide a deep insight into the antiviral response in mIgM⁺ B lymphocytes.

Acute ammonia exposure combined with heat stress impaired the histological features of gills and liver tissues and the expression responses of immune and antioxidative related genes in Nile tilapia

Ammonia exposure can be considered more stressful for aquatic animals when it coincides with high temperature. This study was conducted to detect the effects of ammonia exposure and heat stress and their interactions on the histological features of gills and liver tissues and the expression responses of immune and antioxidative related genes in Nile tilapia. Thus, 180 fish were divided into four groups (triplicates), where the first and third groups were kept in clean water without total ammonium nitrogen (TAN) exposure. At the same time, the second and fourth groups were exposed to 5 mg TAN/L. After seven days, the water temperature was raised in the third (without ammonia toxicity) and fourth (exposed with 5 mg TAN/L) groups up to 32 °C and kept under these conditions for 24 h. While the first (without ammonia toxicity) and second (exposed with 5 mg TAN/L) groups were kept under optimum water temperature (27.28 °C) then gills and liver tissues were dissected. Marked upregulation of keap1 was seen in the gills of fish exposed to ammonia/heat stress. The expression of mRNA levels for nrf2, nqo-1, cat, and gpx genes were downregulated in all stressed groups, with the lowest was recorded in the ammonia/heat stress group. The transcription of ho-1 was upregulated in the ammonia and heat stress groups while downregulated in the ammonia/heat stress group. The transcription of the complement C3 gene was downregulated in the livers of heat stress and ammonia/heat stress groups, while the lysozyme gene was downregulated in the ammonia/heat stress group. The mRNA expression levels of nf-κB, il-1β, and tnf-α genes were higher in the ammonia group than in the heat stress group. The highest transcription level of nf-κB, il-1β, tnf-α, il-8, and hsp70 genes and the lowest C3 and lysozyme genes were observed in fish exposed to ammonia/heat stress. The co-exposure to ammonia with heat stress triggered degeneration of primary and secondary gill filaments with telangiectasia and vascular congestion of secondary epithelium while, the liver showed hepatic vascular congestion and visible necrotic changes with nuclear pyknosis. In conclusion, the combined exposure of ammonia and heat stress induced oxidative stress, immunosuppression, and inflammation in Nile tilapia.

Residual effects of short-term whole-body cold-water immersion on the cytokine profile, white blood cell count, and blood markers of stress

Background: One of the most challenging environmental extremes is immersion in cold/icy water, and consequent common assumption is that even a brief exposure to cold can lead to cold-related illnesses. The increase in the concentrations of the stress hormones cortisol, epinephrine (Epi), and norepinephrine (NE) in response to acute cold stress are thought to suppress the release of proinflammatory cytokines. No previous study has explored the residual consequences of whole-body short-term cold-water immersion (CWI; 14 °C for 10 min) on the immune response in healthy non-acclimated young adult men (aged 20-30 years).Materials and methods: In the current study, we tested the hypothesis that short-term acute whole-body CWI would induce high blood levels of cortisol, NE, and Epi, which in turn would increase circulating leukocyte numbers and delay the production of proinflammatory cytokines (tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6). Results: Short-term whole-body CWI produced a stressful physiological reaction, as manifested by hyperventilation and increased muscle shivering, metabolic heat production, and heart rate. CWI also induced the marked release of the stress hormones Epi, NE, and cortisol. The change in IL-6 concentration after CWI was delayed and TNF-α production was decreased, but IL-1β was not affected within 48 h after CWI. A delayed increase in neutrophil percentage and decrease in lymphocyte percentage occurred after CWI.Conclusion: These findings suggest that, even though CWI caused changes in stress and immune markers, the participants showed no predisposition to symptoms of the common cold within 48 h after CWI.

Recovering body temperature from acute cold stress is associated with delayed proinflammatory cytokine production in vivo

A poor outcome of whole-body hypothermia often results from a late complication, rather than from acute effects of hypothermia. A low body (cell) temperature or the increase in the concentrations of the stress hormones cortisol, epinephrine, and norepinephrine in response to acute cold stress have been proposed as potent proinflammatory cytokine suppressant. In the current study, we tested the hypothesis that the recovery of body temperature from a whole-body intermittent cold-water immersion (CWI, at 13-14 °C for a total 170 min) is associated with a delayed response of proinflammatory cytokines in young healthy men. Our results revealed a delay in the increase in the proinflammatory interleukin 6 and interleukin 1β cytokines after the CWI, which paralleled the changes in cortisol, epinephrine, norepinephrine, and body temperature. CWI decreased tumor necrosis factor α (TNF-α) immediately and 1 h after the CWI. Although TNF-α had recovered to the pre-immersion level at 2 h after CWI, its natural circadian cycle kinetics was disrupted until 12 h after the CWI. Furthermore, we showed that CWI strongly modified the white blood cell counts, with changes reaching a peak between 1 and 2 h after the CWI.

Differential Thermoregulatory and Inflammatory Patterns in the Circadian Response to LPS-Induced Septic Shock

Sepsis is caused by a dysregulated host response to infection, and characterized by uncontrolled inflammation together with immunosuppression, impaired innate immune functions of phagocytes and complement activation. Septic patients develop fever or hypothermia, being the last one characteristic of severe cases. Both lipopolysaccharide (LPS) and Tumor Necrosis Factor (TNF)-α- induced septic shock in mice is dependent on the time of administration. In this study, we aimed to further characterize the circadian response to high doses of LPS. First, we found that mice injected with LPS at ZT11 developed a higher hypothermia than those inoculated at ZT19. This response was accompanied by higher neuronal activation of the preoptic, suprachiasmatic, and paraventricular nuclei of the hypothalamus. However, LPS-induced Tnf-α and Tnf-α type 1 receptor (TNFR1) expression in the preoptic area was time-independent. We also analyzed peritoneal and spleen macrophages, and observed an exacerbated response after ZT11 stimulation. The serum of mice inoculated with LPS at ZT11 induced deeper hypothermia in naïve animals than the one coming from ZT19-inoculated mice, related to higher TNF-α serum levels during the day. We also analyzed the response in TNFR1-deficient mice, and found that both the daily difference in the mortality rate, the hypothermic response and neuronal activation were lost. Moreover, mice subjected to circadian desynchronization showed no differences in the mortality rate throughout the day, and developed lower minimum temperatures than mice under light-dark conditions. Also, those injected at ZT11 showed increased levels of TNF-α in serum compared to standard light conditions. These results suggest a circadian dependency of the central thermoregulatory and peripheral inflammatory response to septic-shock, with TNF-α playing a central role in this circadian response.

Proteasome activator REGγ promotes inflammation in Leydig cells via IkBε signaling

The development of testicular inflammation affects the normal male reproductive function. The proteasome activator complex subunit 3 (REGγ) has been suggested to regulate experimental colitis. However, to the best of our knowledge, a potential association between REGγ and testicular inflammation has not been demonstrated. The present study successfully established inflammatory models in C57 mice, primary Leydig cells and the TM3 cell line. It was observed that the absence of REGγ conveyed a significantly protective effect toward testosterone secretion in Leydig cells. REGγ deficiency significantly decreased the expression levels of phosphorylated transcription factor p65 and inflammatory factors in testis tissues, primary Leydig cells and the TM3 cell line. Inflammation also upregulated the expression levels of REGγ. Furthermore, the degradation of the nuclear factor light‑chain‑enhancer of activated B cells (NF‑κB) inhibitor ε (IkBε) signaling pathway regulated REGγ and NF‑κB expression. Double knockdown of REGγ and IkBε restored the response in wild‑type cells to LPS‑induced inflammation. In summary, these results demonstrated that REGγ regulates NF‑κB activity by specifically degrading IkBε to regulate inflammation in testicular Leydig cells.

Antioxidative, inflammatory and immune responses in hydrogen peroxide-induced liver injury of tilapia (GIFT, Oreochromis niloticus)

Oxidative stress has been implicated in the pathogenesis of many liver diseases in fish, but the molecular mechanism is still obscure. Here, we used hydrogen peroxide (H₂O₂) as a reactive oxygen species (ROS) to induce liver injury and assess underlying molecular mechanism linking oxidative stress and liver injury in fish. Tilapia were injected with various concentrations of H₂O₂ (0, 40, 120, 200, 300 and 400 mM) for 72 h. The blood and liver were collected to assay biochemical parameters and genes expression after 24, 48 and 72 h of injection. The results showed that treatments with higher H₂O₂ levels (300 and/or 400 mM) significantly increased the levels of GPT, GOT, AKP and MDA, and apparently decreased the levels of TP, ALB, SOD, GSH, CAT, GST and T-AOC throughout of the 72 h. The gene expression data showed that treatments with 200, 300 and/or 400 H₂O₂ suppressed Nrf2/keap1 pathway and its downstream genes including ho-1, nqo1 and gsta, activated inflammatory response via enhancing the mRNA levels of nf-κb, tnf-α, il-1β and il-8, and attenuating il-10 mRNA level, and caused immunotoxicity through downregulating the genes expression of c3, hep, lzm and Igm for 24, 48 and/or 72 h. Additionally, there was a mild or strong increase in levels of nrf2 and its subsequent antioxidant genes or enzymes such as ho-1, nqo1, gst, CAT and SOD in treatments with lower concentrations of H₂O₂ (40 or 120 mM) for 24 and/or 48 h. Overall results suggested that H₂O₂ hepatotoxicity was mainly concerned with lipid peroxidation, impairment antioxidant defense systems, inflammatory response and immunotoxicity, and Nrf2/Keap1 and NF-κB signaling pathways played important roles in oxidative stress-induced liver injury in fish.

The Efficacy of the Interferon Alpha/Beta Response versus Arboviruses Is Temperature Dependent

Interferon alpha/beta (IFN-α/β) is a critical mediator of protection against most viruses, with host survival frequently impossible in its absence. Many studies have investigated the pathways involved in the induction of IFN-α/β after virus infection and the resultant upregulation of antiviral IFN-stimulated genes (ISGs) through IFN-α/β receptor complex signaling. However, other than examining the effects of genetic deletion of induction or effector pathway components, little is known regarding the functionality of these responses in intact hosts and whether host genetic or environmental factors might influence their potency. Here, we demonstrate that the IFN-α/β response against multiple arthropod-vectored viruses, which replicate over a wide temperature range, is extremely sensitive to fluctuations in temperature, exhibiting reduced antiviral efficacy at subnormal cellular temperatures and increased efficacy at supranormal temperatures. The effect involves both IFN-α/β and ISG upregulation pathways with a major aspect of altered potency reflecting highly temperature-dependent transcription of IFN response genes that leads to altered IFN-α/β and ISG protein levels. Discordantly, signaling steps prior to transcription that were examined showed the opposite effect from gene transcription, with potentiation at low temperature and inhibition at high temperature. Finally, we demonstrate that by lowering the temperature of mice, chikungunya arbovirus replication and disease are exacerbated in an IFN-α/β-dependent manner. This finding raises the potential for use of hyperthermia as a therapeutic modality for viral infections and in other contexts such as antitumor therapy. The increased IFN-α/β efficacy at high temperatures may also reflect an innate immune-relevant aspect of the febrile response.

The interferon alpha/beta (IFN-α/β) response is a first-line innate defense against arthropod-borne viruses (arboviruses). Arboviruses, such as chikungunya virus (CHIKV), can infect cells and replicate across a wide temperature range due to their replication in both mammalian/avian and arthropod hosts. Accordingly, these viruses can cause human disease in tissues regularly exposed to temperatures below the normal mammalian core temperature, 37°C. We questioned whether temperature variation could affect the efficacy of IFN-α/β responses against these viruses and help to explain some aspects of human disease manifestations. We observed that IFN-α/β efficacy was dramatically lower at subnormal temperatures and modestly enhanced at febrile temperatures, with the effects involving altered IFN-α/β response gene transcription but not IFN-α/β pathway signaling. These results provide insight into the functioning of the IFN-α/β response in vivo and suggest that temperature elevation may represent an immune-enhancing therapeutic modality for a wide variety of IFN-α/β-sensitive infections and pathologies.

Hypothermia and brain inflammation after cardiac arrest

The cessation (ischemia) and restoration (reperfusion) of cerebral blood flow after cardiac arrest (CA) induce inflammatory processes that can result in additional brain injury. Therapeutic hypothermia (TH) has been proven as a brain protective strategy after CA. In this article, the underlying pathophysiology of ischemia-reperfusion brain injury with emphasis on the role of inflammatory mechanisms is reviewed. Potential targets for immunomodulatory treatments and relevant effects of TH are also discussed. Further studies are needed to delineate the complex pathophysiology and interactions among different components of immune response after CA and identify appropriate targets for clinical investigations.

Effect of Trichilia monadelpha (Meliaceae) extracts on bone histomorphology in complete Freund's adjuvant-induced arthritis

AIM

This study aimed to assess the effect of petroleum ether extract (PEE), ethyl acetate extract (EthE), and ethanol extract (EAE) of Trichilia monadelpha stem bark on bone histomorphology in arthritis.

METHODS

Percentage inhibition of edema and arthritic scores in complete Freund's adjuvant-induced (0.1 ml of 5 mg/ml¹ of heat-killed Mycobacterium tuberculosis in paraffin oil-injected subplantar into the right hind paw) arthritic Sprague-Dawley rats treated with PEE, EthE, or EAE (10,30, and 100 mg/kg¹, respectively), dexamethasone (0.3-3.0 mg/kg¹), or methotrexate (0.1-1.0 mg/kg¹) over a 28-day period were estimated. Rat paws were radiographed and scored. Body weights were taken and paw tissues were harvested for histopathological studies.

RESULTS

The extracts significantly (P ≤ 0.01-0.0001) and dose dependently reduced the polyarthritic phase of arthritis. EAE and PEE significantly (P ≤ 0.01-0.0001) minimized edema spread from acute arthritic phase (days 0-10) to polyarthritic phase (days 10-28). EthE improved which deteriorated body weight in arthritis. All extracts significantly (P ≤ 0.05-0.01) improved arthritic score; reducing erythema, swelling and joint rigidity, and also significantly (P ≤ 0.05-0.01) reduced hyperplasia, pannus formation, and exudation of inflammatory cells into synovial spaces.

CONCLUSION

The stem bark extracts of T. monadelpha reduce bone tissue damage and resorption associated with adjuvant-induced arthritis, hence could be useful in managing arthritis in humans.

Effects of Hyperoxia and Mild Therapeutic Hypothermia During Resuscitation From Porcine Hemorrhagic Shock

OBJECTIVE

Hemorrhagic shock-induced tissue hypoxia induces hyperinflammation, ultimately causing multiple organ failure. Hyperoxia and hypothermia can attenuate tissue hypoxia due to increased oxygen supply and decreased demand, respectively. Therefore, we tested the hypothesis whether mild therapeutic hypothermia and hyperoxia would attenuate postshock hyperinflammation and thereby organ dysfunction.

DESIGN

Prospective, controlled, randomized study.

SETTING

University animal research laboratory.

SUBJECTS

Thirty-six Bretoncelles-Meishan-Willebrand pigs of either gender.

INTERVENTIONS

After 4 hours of hemorrhagic shock (removal of 30% of the blood volume, subsequent titration of mean arterial pressure at 35 mm Hg), anesthetized and instrumented pigs were randomly assigned to "control" (standard resuscitation: retransfusion of shed blood, fluid resuscitation, norepinephrine titrated to maintain mean arterial pressure at preshock values, mechanical ventilation titrated to maintain arterial oxygen saturation > 90%), "hyperoxia" (standard resuscitation, but FIO2, 1.0), "hypothermia" (standard resuscitation, but core temperature 34°C), or "combi" (hyperoxia plus hypothermia) (n = 9 each).

MEASUREMENTS AND MAIN RESULTS

Before, immediately at the end of and 12 and 22 hours after hemorrhagic shock, we measured hemodynamics, blood gases, acid-base status, metabolism, organ function, cytokine production, and coagulation. Postmortem kidney specimen were taken for histological evaluation, immunohistochemistry (nitrotyrosine, cystathionine γ-lyase, activated caspase-3, and extravascular albumin), and immunoblotting (nuclear factor-κB, hypoxia-inducible factor-1α, heme oxygenase-1, inducible nitric oxide synthase, B-cell lymphoma-extra large, and protein expression of the endogenous nuclear factor-κB inhibitor). Although hyperoxia alone attenuated the postshock hyperinflammation and thereby tended to improve visceral organ function, hypothermia and combi treatment had no beneficial effect.

CONCLUSIONS

During resuscitation from near-lethal hemorrhagic shock, hyperoxia attenuated hyperinflammation, and thereby showed a favorable trend toward improved organ function. The lacking efficacy of hypothermia was most likely due to more pronounced barrier dysfunction with vascular leakage-induced circulatory failure.

Shifts in temperature within the physiologic range modify strand-specific expression of select human microRNAs

Previous studies have revealed that clinically relevant changes in temperature modify clinically relevant gene expression profiles through transcriptional regulation. Temperature dependence of post-transcriptional regulation, specifically, through expression of miRNAs has been less studied. We comprehensively analyzed the effect of 24 h exposure to 32°C or 39.5°C on miRNA expression profile in primary cultured human small airway epithelial cells (hSAECs) and its impact on expression of a targeted protein, protein kinase C α (PKCα). Using microarray, and solution hybridization-based nCounter assays, with confirmation by quantitative RT-PCR, we found significant temperature-dependent changes in expression level of only five mature human miRNAs, representing only 1% of detected miRNAs. Four of these five miRNAs are the less abundant passenger (star) strands. They exhibited a similar pattern of increased expression at 32°C and reduced expression at 39.5°C relative to 37°C. As PKCα mRNA has multiple potential binding sites for three of these miRNAs, we analyzed PKCα protein expression in HEK 293T cells and hSAECs. PKCα protein levels were lowest at 32°C and highest at 39.5°C and specific miRNA inhibitors reduced these effects. Finally, we analyzed cell-cycle progression in hSAECs and found 32°C cells exhibited the greatest G1 to S transition, a process known to be inhibited by PKCα, and the effect was mitigated by specific miRNA inhibitors. These results demonstrate that exposure to clinically relevant hypothermia or hyperthermia modifies expression of a narrow subset of miRNAs and impacts expression of at least one signaling protein involved in multiple important cellular processes.

Therapeutic hypothermia after nonshockable cardiac arrest: the HYPERION multicenter, randomized, controlled, assessor-blinded, superiority trial

BACKGROUND

Meta-analyses of nonrandomized studies have provided conflicting data on therapeutic hypothermia, or targeted temperature management (TTM), at 33°C in patients successfully resuscitated after nonshockable cardiac arrest. Nevertheless, the latest recommendations issued by the International Liaison Committee on Resuscitation and by the European Resuscitation Council recommend therapeutic hypothermia. New data are available on the adverse effects of therapeutic hypothermia, notably infectious complications. The risk/benefit ratio of therapeutic hypothermia after nonshockable cardiac arrest is unclear.

METHODS

HYPERION is a multicenter (22 French ICUs) trial with blinded outcome assessment in which 584 patients with successfully resuscitated nonshockable cardiac arrest are allocated at random to either TTM between 32.5 and 33.5°C (therapeutic hypothermia) or TTM between 36.5 and 37.5°C (therapeutic normothermia) for 24 hours. Both groups are managed with therapeutic normothermia for the next 24 hours. TTM is achieved using locally available equipment. The primary outcome is day-90 neurological status assessed by the Cerebral Performance Categories (CPC) Scale with dichotomization of the results (1 + 2 versus 3 + 4 + 5). The primary outcome is assessed by a blinded psychologist during a semi-structured telephone interview of the patient or next of kin. Secondary outcomes are day-90 mortality, hospital mortality, severe adverse events, infections, and neurocognitive performance. The planned sample size of 584 patients will enable us to detect a 9% absolute difference in day-90 neurological status with 80% power, assuming a 14% event rate in the control group and a two-sided Type 1 error rate of 4.9%. Two interim analyses will be performed, after inclusion of 200 and 400 patients, respectively.

DISCUSSION

The HYPERION trial is a multicenter, randomized, controlled, assessor-blinded, superiority trial that may provide an answer to an issue of everyday relevance, namely, whether TTM is beneficial in comatose patients resuscitated after nonshockable cardiac arrest. Furthermore, it will provide new data on the tolerance and adverse events (especially infectious complications) of TTM at 32.5-33.5°C.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01994772 .

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.

MicroRNA-155 potentiates the inflammatory response in hypothermia by suppressing IL-10 production

Therapeutic hypothermia is commonly used to improve neurological outcomes in patients after cardiac arrest. However, therapeutic hypothermia increases sepsis risk and unintentional hypothermia in surgical patients increases infectious complications. Nonetheless, the molecular mechanisms by which hypothermia dysregulates innate immunity are incompletely understood. We found that exposure of human monocytes to cold (32°C) potentiated LPS-induced production of TNF and IL-6, while blunting IL-10 production. This dysregulation was associated with increased expression of microRNA-155 (miR-155), which potentiates Toll-like receptor (TLR) signaling by negatively regulating Ship1 and Socs1. Indeed, Ship1 and Socs1 were suppressed at 32°C and miR-155 antagomirs increased Ship1 and Socs1 and reversed the alterations in cytokine production in cold-exposed monocytes. In contrast, miR-155 mimics phenocopied the effects of cold exposure, reducing Ship1 and Socs1 and altering TNF and IL-10 production. In a murine model of LPS-induced peritonitis, cold exposure potentiated hypothermia and decreased survival (10 vs. 50%; P < 0.05), effects that were associated with increased miR-155, suppression of Ship1 and Socs1, and alterations in TNF and IL-10. Importantly, miR-155-deficiency reduced hypothermia and improved survival (78 vs. 32%, P < 0.05), which was associated with increased Ship1, Socs1, and IL-10. These results establish a causal role of miR-155 in the dysregulation of the inflammatory response to hypothermia.

Unintentional perioperative hypothermia is associated with severe complications and high mortality in elective operations

INTRODUCTION

Hypothermia occurs in as many as 7% of elective colorectal operations and is an underestimated risk factor for complications and death. Rewarming of hypothermic patients alone is not sufficient to prevent such adverse events. We investigated the outcomes of patients who became hypothermic (<35°C) after elective operations and compared them with closely matched, nonhypothermic operative patients to better define the impact of hypothermia on surgical outcomes, as well as to identify independent risk factors for hypothermia.

METHODS

We queried the University HealthSystem Consortium (UHC) database for elective operative patients who became unintentionally hypothermic from October 2008 to March 2012, and identified 707 patients. Exclusion criteria were deliberate hypothermia, age <18 years, or death on day of admission. Separately, to validate the accuracy of hypothermia coding, we reviewed the hospital charts of all University of Louisville Hospital patients with hypothermia whose data were submitted to UHC.

RESULTS

All patients from UHC with a code for hypothermia were indeed unintentionally hypothermic. Hypothermic patients undergoing elective operations experienced a 4-fold increase in mortality (17.0% vs 4.0%; P < .001) and a doubled complication rate (26.3% vs 13.9%; P < .001), in which sepsis and stroke increased the most. Several independent risk factors for hypothermia were amenable to preoperative improvement: anemia, chronic renal impairment, and unintended weight loss. Severity of illness on admission, age >65 years, male sex, and neurologic disorders also were risk factors.

CONCLUSION

Hypothermia is associated with an increased rate of mortality and complications. Preventive treatment of these risk factors before operation and aggressive warming measures in the "at risk" population may decrease hypothermia-related morbidity and mortality in elective operations. Randomized-controlled trials should be conducted to evaluate the impact of aggressive warming measures in the at-risk population.

Non-pharmaceutical therapies for stroke: mechanisms and clinical implications

Stroke is deemed a worldwide leading cause of neurological disability and death, however, there is currently no promising pharmacotherapy for acute ischemic stroke aside from intravenous or intra-arterial thrombolysis. Yet because of the narrow therapeutic time window involved, thrombolytic application is very restricted in clinical settings. Accumulating data suggest that non-pharmaceutical therapies for stroke might provide new opportunities for stroke treatment. Here we review recent research progress in the mechanisms and clinical implications of non-pharmaceutical therapies, mainly including neuroprotective approaches such as hypothermia, ischemic/hypoxic conditioning, acupuncture, medical gases and transcranial laser therapy. In addition, we briefly summarize mechanical endovascular recanalization devices and recovery devices for the treatment of the chronic phase of stroke and discuss the relative merits of these devices.

Alternative promoters regulate cold inducible RNA-binding (CIRP) gene expression and enhance transgene expression in mammalian cells

The use of a temperature shift cultivation to enhance recombinant protein yield is widely utilised in the bioprocessing industry. The responses of mammalian cells to heat stress are well characterized; however, the equivalent cold stress responses are not. In particular, the transcriptional mechanisms that lead to enhanced gene-specific expression upon cold stress have yet to be elucidated. We report here in silico and experimental identification and characterization of transcriptional control elements that regulate cold inducible RNA-binding (CIRP) gene expression and demonstrate these can be used for enhanced transgene expression. In silico analysis identified the core CIRP promoter and a number of conserved transcription factor-binding sites across mammalian species. The core promoter was confirmed by experimental studies that located the basal transcriptional regulatory elements of CIRP within 264 nucleotides upstream of the transcription start site. Deletion analysis of a fragment from -264 to -64 that contained two putative CAAT-binding sites abolished promoter activity. A second promoter was identified in the region -452 to -264 of the transcription start site which was able to drive transcription independent of the core promoter. As the two CIRP promoters were transcriptionally active and possibly cold responsive, we used electrophoretic mobility shift assays to show that both promoter regions are able to bind factors within a nuclear extract in a dose-dependent manner and that the formation of these complexes was specific to the promoter regions. Finally, we successfully demonstrate using a reporter gene approach that enhanced transgene expression can be achieved using the identified CIRP promoter.

Hydrogen sulfide donor NaHS reduces organ injury in a rat model of pneumococcal pneumosepsis, associated with improved bio-energetic status

Sepsis is characterized by a generalized inflammatory response and organ failure, associated with mitochondrial dysfunction. Hydrogen sulfide donor NaHS has anti-inflammatory properties, is able to reduce metabolism and can preserve mitochondrial morphology and function. Rats were challenged with live Streptococcus pneumonia or saline and infused with NaHS (36 µmol/kg/h) or vehicle. Lung and kidney injury markers were measured as well as mitochondrial function, viability and biogenesis. Infusion of NaHS reduced heart rate and body temperature, indicative of a hypo-metabolic state. NaHS infusion reduced sepsis-related lung and kidney injury, while host defense remained intact, as reflected by unchanged bacterial outgrowth. The reduction in organ injury was associated with a reversal of a fall in active oxidative phosphorylation with a concomitant decrease in ATP levels and ATP/ADP ratio. Preservation of mitochondrial respiration was associated with increased mitochondrial expression of α-tubulin and protein kinase C-ε, which acts as regulators of respiration. Mitochondrial damage was decreased by NaHS, as suggested by a reduction in mitochondrial DNA leakage in the lung. Also, NaHS treatment was associated with upregulation of peroxisome proliferator-activated receptor-γ coactivator 1α, with a subsequent increase in transcription of mitochondrial respiratory subunits. These findings indicate that NaHS reduces organ injury in pneumosepsis, possibly via preservation of oxidative phosphorylation and thereby ATP synthesis as well as by promoting mitochondrial biogenesis. Further studies on the involvement of mitochondria in sepsis are required.

Biomarkers as predictors of outcome after cardiac arrest

Cardiac arrest (CA) is a major health and economic problem. Management of patients resuscitated from CA is challenging for clinicians, and the mortality rate of those who achieve return of spontaneous circulation remains high. Hypoxic brain injury, cardiovascular abnormalities and systemic ischemia/reperfusion response characterize the so-called 'postcardiac arrest syndrome', which could lead to multiple organ failure and poor outcome after CA. The magnitude of these disorders differs in individual patients, mainly based on the cause and duration of CA and on the severity of the ischemic episode. Prognostication of outcome after CA is of importance because it could help physicians on triage decisions and readdress the overall management. A number of factors are thought to influence the prognosis of patients after CA, but due to the heterogeneity of CA population and scenarios no single factor has been identified as a reliable predictor of outcome and the timing and optimal approach to prognostication is still controversial. Biomarkers represent a growing area of interest in this field, as they may provide clinicians with early information on the severity of organ dysfunction to make a decision on clinical strategies and prognosticate outcome. In this article, the authors will focus on cardiac, neurological and inflammatory biomarkers as potential predictors of outcome after CA.

Temperature-induced transcription of inflammatory mediators and the influence of Hsp70 following LPS stimulation of southern bluefin tuna peripheral blood leukocytes and kidney homogenates

Temperature is known to influence inflammatory signalling in mammals, but far less understood in fish. The aim of the present study was to explore the potential effects of temperature on innate immune signalling in head kidney and leukocyte populations of the economically important southern bluefin tuna through the identification and utilization of gene expression targets in vitro. Here, we identified the mRNA sequences of five potential inflammatory mediators - TNFα (1 and 2), IL-1β, IL-8, and Cox2 - and demonstrate induction of four - TNFα (2), IL-1β, IL-8, and Cox2 - following LPS stimulation of both peripheral blood leukocytes and head kidney homogenates in vitro by real-time quantitative PCR. Comparison of transcriptional expression in cultures held at 18 and 25 °C (both within the presumed natural temperature range of this heterothermic species) showed accelerated transcription of cytokines TNFα, IL-1β and IL-8 following LPS stimulation at 25 °C in both tissue types. Peak induction reached comparable levels for each transcript at both temperatures during the 24 h test period with only limited (if any) protraction in expression resulting from cold temperature (18 °C) incubation. Partial mRNA sequences were also identified for both the constitutively expressed and heat inducible chaperone proteins Hsc70 and Hsp70, and 24 h incubation at 25 °C was sufficient to induce Hsp70 transcription in leukocyte but not in head kidney cell populations. Taken together these findings suggest that temperature exerts influence in the timing but not the degree of an innate inflammatory response in bluefin tuna and that different cell populations have differential responsiveness to heat shock in this heterothermic species. Further, LPS stimulation failed to induce Hsp70 at either incubation temperature in leukocytes; whereas 25 °C incubation caused Hsp70 up-regulation in leukocytes with or without the presence of LPS. This suggests that Hsp70 does not play a direct role in immune responsiveness for this species and that an environmental temperature of 25 °C in excess of 24 h initiates a cellular stress response in blood cells of this organism. Lastly, a strong correlation between Hsp70 and IL-8 transcriptional expression was observed following LPS/heat shock stimulation of leukocytes and five potential heat shock response elements were subsequently identified on the gene promoter region of IL-8 indicating that heat shock co-activation of this chemokine previously identified in mammals is also likely present in fish.

Molecular and cellular pathways as a target of therapeutic hypothermia: pharmacological aspect

Induced therapeutic hypothermia is the one of the most effective tools against brain injury and inflammation. Even though its beneficial effects are well known, there are a lot of pitfalls to overcome, since the potential adverse effects of systemic hypothermia are still troublesome. Without the knowledge of the precise mechanisms of hypothermia, it will be difficult to tackle the application of hypothermia in clinical fields. Better understanding of the characteristics and modes of hypothermic actions may further extend the usage of hypothermia by developing novel drugs based on the hypothermic mechanisms or by combining hypothermia with other therapeutic modalities such as neuroprotective drugs. In this review, we describe the potential therapeutic targets for the development of new drugs, with a focus on signal pathways, gene expression, and structural changes of cells. Theapeutic hypothermia has been shown to attenuate neuroinflammation by reducing the production of reactive oxygen species and proinflammatory mediators in the central nervous system. Along with the mechanism-based drug targets, applications of therapeutic hypothermia in combination with drug treatment will also be discussed in this review.

Implication for long-term hypothermia on degradation of interleukin-8 mRNA in endothelial cells stimulated with lipopolysaccharides

This experimental study investigated the effects of long-term hypothermia on the production of interleukin (IL)-8 protein and its mRNA expression in endothelial cells stimulated by lipopolysaccharides (LPS). Human umbilical vein endothelial cells were separated into a non-cooling group (N group: 37°C) and a cooling group (C group: 30°C). These groups were incubated with LPS (1 μg/mL) for 0, 2, 6, 24, 48, 72, and 96 hours. Production of the IL-8 protein secreted into the supernatant and mRNA expression in the cells were measured using enzyme-linked immunoabsorbent assay (ELISA) and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. To evaluate mRNA stability, both groups were incubated with actinomycin D at 6 hours after incubation with LPS for 24 hours. The degradation ratio was calculated by comparing the total expression of mRNA at 6 hours versus 0 hours. The protein levels in the C group were significantly lower than the N group between 6 and 96 hours. The mRNA expression in the C group was also significantly lower than in the N group up to 48 hours, but at 72 hours it was significantly higher than N group. IL-8 mRNA was less degraded in the C group compared to the N group. Under long-term hypothermia, IL-8 protein production was suppressed, while IL-8 mRNA was stabilized after LPS treatment. The potential of IL-8 to produce an inflammatory response in endothelial cells may persist even during long-term hypothermia.

Naturally occurring hypothermia is more advantageous than fever in severe forms of lipopolysaccharide- and Escherichia coli-induced systemic inflammation

The natural switch from fever to hypothermia observed in the most severe cases of systemic inflammation is a phenomenon that continues to puzzle clinicians and scientists. The present study was the first to evaluate in direct experiments how the development of hypothermia vs. fever during severe forms of systemic inflammation impacts the pathophysiology of this malady and mortality rates in rats. Following administration of bacterial lipopolysaccharide (LPS; 5 or 18 mg/kg) or of a clinical Escherichia coli isolate (5 × 10(9) or 1 × 10(10) CFU/kg), hypothermia developed in rats exposed to a mildly cool environment, but not in rats exposed to a warm environment; only fever was revealed in the warm environment. Development of hypothermia instead of fever suppressed endotoxemia in E. coli-infected rats, but not in LPS-injected rats. The infiltration of the lungs by neutrophils was similarly suppressed in E. coli-infected rats of the hypothermic group. These potentially beneficial effects came with costs, as hypothermia increased bacterial burden in the liver. Furthermore, the hypotensive responses to LPS or E. coli were exaggerated in rats of the hypothermic group. This exaggeration, however, occurred independently of changes in inflammatory cytokines and prostaglandins. Despite possible costs, development of hypothermia lessened abdominal organ dysfunction and reduced overall mortality rates in both the E. coli and LPS models. By demonstrating that naturally occurring hypothermia is more advantageous than fever in severe forms of aseptic (LPS-induced) or septic (E. coli-induced) systemic inflammation, this study provides new grounds for the management of this deadly condition.

Mild hypothermia reduces ventilator-induced lung injury, irrespective of reducing respiratory rate

In the era of lung-protective mechanical ventilation using limited tidal volumes, higher respiratory rates are applied to maintain adequate minute volume ventilation. However, higher respiratory rates may contribute to ventilator-induced lung injury (VILI). Induced hypothermia reduces carbon dioxide production and might allow for lower respiratory rates during mechanical ventilation. We hypothesized that hypothermia protects from VILI and investigated whether reducing respiratory rates enhance lung protection in an in vivo model of VILI. During 4 h of mechanical ventilation, VILI was induced by tidal volumes of 18 mL/kg in rats, with respiratory rates set at 15 or 10 breaths/min in combination with hypothermia (32°C) or normothermia (37°C). Hypothermia was induced by external cooling. A physiologic model was established. VILI was characterized by increased pulmonary neutrophil influx, protein leak, wet weights, histopathology score, and cytokine levels compared with lung protective mechanical ventilation. Hypothermia decreased neutrophil influx, pulmonary levels, systemic interleukin-6 levels, and histopathology score, and it tended to decrease the pulmonary protein leak. Reducing the respiratory rate in combination with hypothermia did not reduce the parameters of the lung injury. In conclusion, hypothermia protected from lung injury in a physiologic VILI model by reducing inflammation. Decreasing the respiratory rate mildly did not enhance protection.

Dysfunctional nucleus tractus solitarius: its crucial role in promoting neuropathogenetic cascade of Alzheimer's dementia--a novel hypothesis

The pathophysiological mechanism(s) underlying Alzheimer's disease (AD) still remain unclear, and no disease-modifying or prophylactic therapies are currently available. Unraveling the fundamental neuropathogenesis of AD is an important challenge. Several studies on AD have suggested lesions in a number of CNS areas including the basal forebrain, hippocampus, entorhinal cortex, amygdale/insula, and the locus coeruleus. However, plausible unifying studies on the upstream factors that involve these heterogeneous regions and herald the onset of AD pathogenesis are not available. The current article presents a novel nucleus tractus solitarius (NTS) vector hypothesis that underpins several disparate biological mechanisms and neural circuits, and identifies relevant hallmarks of major presumptive causative factor(s) linked to the NTS, in older/aging individuals. Aging, obesity, infection, sleep apnea, smoking, neuropsychological states, and hypothermia-all activate inflammatory cytokines and oxidative stress. The synergistic impact of systemic proinflammatory mediators activates microglia and promotes neuroinflammation. Acutely, the innate immune response is protective defending against pathogens/toxins; however, when chronic, it causes neuroinflammation and neuronal dysfunction, particularly in brainstem and neocortex. The NTS in the brainstem is an essential multiple signaling hub, and an extremely important central integration site of baroreceptor, chemoreceptor, and a multitude of sensory afferents from gustatory, gastrointestinal, cardiac, pulmonary, and upper airway systems. Owing to persistent neuroinflammation, the dysfunctional NTS exerts deleterious impact on nucleus ambiguus, dorsal motor nucleus of vagus, hypoglossal, parabrachial, locus coeruleus and many key nuclei in the brainstem, and the hippocampus, entorhinal cortex, prefrontal cortex, amygdala, insula, and basal forebrain in the neocortex. The neuronal and synaptic dysfunction emanating from the inflamed NTS may affect its interconnected pathways impacting almost the entire CNS--which is already primed by neuroinflammation, thus promoting cognitive and neuropsychiatric symptoms. The upstream factors discussed here may underpin the neuropathopgenesis of AD. AD pathology is multifactorial; the current perspective underscores the value of attenuating disparate upstream factors--in conjunction with anticholinesterase, anti-inflammatory, immunosuppressive, and anti-oxidant pharmacotherapy. Amelioration of the NTS pathology may be of central importance in countering the neuropathological cascade of AD. The NTS, therefore, may be a potential target of novel therapeutic strategies.

Pilot randomized trial of therapeutic hypothermia with serial cranial ultrasound and 18-22 month follow-up for neonatal encephalopathy in a low resource hospital setting in Uganda: study protocol

Background

There is now convincing evidence that in industrialized countries therapeutic hypothermia for perinatal asphyxial encephalopathy increases survival with normal neurological function. However, the greatest burden of perinatal asphyxia falls in low and mid-resource settings where it is unclear whether therapeutic hypothermia is safe and effective.

Aims

Under the UCL Uganda Women's Health Initiative, a pilot randomized controlled trial in infants with perinatal asphyxia was set up in the special care baby unit in Mulago Hospital, a large public hospital with ~20,000 births in Kampala, Uganda to determine:

(i) The feasibility of achieving consent, neurological assessment, randomization and whole body cooling to a core temperature 33-34°C using water bottles

(ii) The temperature profile of encephalopathic infants with standard care

(iii) The pattern, severity and evolution of brain tissue injury as seen on cranial ultrasound and relation with outcome

(iv) The feasibility of neurodevelopmental follow-up at 18-22 months of age

Methods/Design

Ethical approval was obtained from Makerere University and Mulago Hospital. All infants were in-born. Parental consent for entry into the trial was obtained. Thirty-six infants were randomized either to standard care plus cooling (target rectal temperature of 33-34°C for 72 hrs, started within 3 h of birth) or standard care alone. All other aspects of management were the same. Cooling was performed using water bottles filled with tepid tap water (25°C). Rectal, axillary, ambient and surface water bottle temperatures were monitored continuously for the first 80 h. Encephalopathy scoring was performed on days 1-4, a structured, scorable neurological examination and head circumference were performed on days 7 and 17. Cranial ultrasound was performed on days 1, 3 and 7 and scored. Griffiths developmental quotient, head circumference, neurological examination and assessment of gross motor function were obtained at 18-22 months.

Discussion

We will highlight differences in neonatal care and infrastructure that need to be taken into account when considering a large safety and efficacy RCT of therapeutic hypothermia in low and mid resource settings in the future.

Trial registration

Current controlled trials ISRCTN92213707

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.

Whole body hypothermia broadens the therapeutic window of intranasally administered IGF-1 in a neonatal rat model of cerebral hypoxia-ischemia

To investigate whether whole body hypothermia after neonatal cerebral hypoxia-ischemia (HI) could broaden the therapeutic window of intranasal treatment of IGF-1 (iN-IGF-1), postnatal day 7 rat pups were subjected to right common carotid artery ligation, followed by 8% oxygen inhalation for 2h. After HI, one group of pups were returned to their dams and kept at room temperature (24.5±0.2°C). A second group of pups were subjected to whole body hypothermia in a cool environment (21.5±0.3°C) for 2 or 4h before being returned to their dams. Two doses of 50 μg recombinant human IGF-1 were administered intranasally at a 1h interval starting at 0, 2 or 4h after hypothermia. Hypothermia decreased the rectal temperature of pups by 4.5°C as compared to those kept at room temperature. While hypothermia or iN-IGF-1 administered 2h after HI alone did not provide neuroprotection, the combined treatment of hypothermia with iN-IGF-1 significantly protected the neonatal rat brain from HI injury. Hypothermia treatment extended the therapeutic window of IGF-1 to 6h after HI. The extended IGF-1 therapeutic window by hypothermia was associated with decreases in infiltration of polymorphonuclear leukocytes and activation of microglia/macrophages and with attenuation of NF-κB activation in the ipsilateral hemisphere following HI.

[Importance of hypothermia in multiple trauma patients]

Multiple trauma patients frequently demonstrate a hypothermic core temperature, defined as a temperature below 35 degrees C, already at admission in the emergency room. As a drop of the core temperature below 34 degrees C has been shown to be associated with a significant increase in post-traumatic complications, this limit is considered to be critical in these patients. Multiple trauma patients with hypothermia demonstrate a markedly increased mortality rate compared to normothermic patients with the same injury severity. Therefore effective rewarming measures are essential for adequate bleeding control and successful resuscitation. If and to what extent the induction of controlled hypothermia in the early phase of treatment on the intensive care unit after resuscitation and operative bleeding control can contribute to an improved post-traumatic outcome, has to be clarified in further experimental and clinical studies.

Serum procalcitonin, C-reactive protein and white blood cell levels following hypothermia after cardiac arrest: a retrospective cohort study

INTRODUCTION

The aim of this study was to investigate time course of procalcitonin (PCT), C-reactive protein (CRP) and white blood cell (WBC) levels in patients with therapeutic hypothermia after cardiac arrest.

METHODS

We retrospectively assessed laboratory and clinical data in a consecutive cohort of patients admitted to the medical intensive-care-unit of the University Hospital in Basel, Switzerland, in whom therapeutic hypothermia was induced because of cardiac arrest between December 2007 and January 2009. Infection was considered based on microbiological evidence (restricted definition) and/or clinical evidence of infection with prescription of antibiotics (extended definition).

RESULTS

From 34 included patients, 25 had respiratory tract infection based on the clinical judgment and in 18 microbiological cultures turned positive (restricted definition). PCT concentrations were highest on the first day after hypothermia and showed a steady decrease until day 7 without differences in patients with and without presumed infection. CRP concentrations increased to a peak level at days 3-4 followed by a steady decrease; CRP concentrations were higher in patients with clinical diagnosis of infection on day 4 (P = 0.02); and in patients with evidence of bacterial growth in cultures on days 4 and 5 (P = 0.01 and P = 0.006). WBC remained unchanged after hypothermia without differences between patients with and without infection.

CONCLUSION

High initial values of PCT and high peak levels after 3-4 days of CRP were found in patients with induction of hypothermia after cardiac arrest. This increase was unspecific and mirrors rather an inflammatory reaction than true underlying infection, limiting the diagnostic potential for early antibiotic stewardship in these patients.

Tumor necrosis factor-α increases the paracellular permeability of Caco-2 cell monolayers in vitro

AIM: To investigate the effects of tumor necrosis factor-α (TNF-α) on the paracellular permeability of Caco-2 cell monolayers and to explore potential mechanisms involved.

METHODS: Caco-2 cells were cultured in vitro to establish a model of intestinal epithelial barrier and divided randomly into two groups: control group and TNF-α treatment group. The TNF-α treatment group was further divided into four subgroups for testing at 3, 6, 12 and 24 h after TNF-α treatment. The changes in transepithelial electrical resistance (TEER) of Caco-2 cells were measured using an electrical resistance system. The changes in cytoskeleton were observed by direct staining with rhodamine-phalloidin. The activation of nuclear factor-κB (NF-κB) was determined by luciferase reporter gene assay.

RESULTS: The TEER significantly decreased in all four treatment subgroups compared to the control group (all P < 0.05). The TEER was significantly lower in the 24-h treatment subgroup than in other subgroups (all P < 0.05). The activation level of NF-κB was significantly raised in 3-, 6- and 12-h treatment subgroups compared to the control group (all P < 0.05). The activation level of NF-κB in 12-h treatment subgroup was significantly higher than those in other subgroups (all P < 0.05). In the control group, rhodamine-phalloidin staining showed that F-actin was visualized around the cell membrane and exhibited a honeycomb pattern of fluorescent staining. After treatment with TNF-α, the fluorescence signals were weakened and distributed in a serrated pattern.

CONCLUSION: TNF-α increases the paracellular permeability of Caco-2 cell monolayers perhaps by inducing NF-κB activation and actin reorganization.

Plasma and myocardial visfatin expression changes are associated with therapeutic hypothermia protection during murine hemorrhagic shock/resuscitation

AIM

Cytokine production during hemorrhagic shock (HS) could affect cardiac function during the hours after resuscitation. Visfatin is a recently described protein that functions both as a proinflammatory plasma cytokine and an intracellular enzyme within the nicotinamide adenine dinucleotide (NAD(+)) salvage pathway. We developed a mouse model of HS to study the effect of therapeutic hypothermia (TH) on hemodynamic outcomes and associated plasma and tissue visfatin content.

METHODS

Mice were bled and maintained at a mean arterial pressure (MAP) of 35 mmHg. After 30 min, animals (n=52) were randomized to normothermia (NT, 37+/-0.5 degrees C) or TH (33+/-0.5 degrees C) followed by rewarming at 60 min following resuscitation. After 90 min of HS (S90), mice were resuscitated and monitored for 180 min (R180). Visfatin, interleukin 6 (IL-6), keratinocyte-derived chemokine (KC), tumor necrosis factor-alpha (TNF-alpha), and myoglobin were measured by ELISA.

RESULTS

Compared to NT, TH animals exhibited improved R180 survival (23/26 [88.5%] vs. 13/26 [50%]; p=0.001). Plasma visfatin, IL-6, KC, and TNF-alpha increased by S90 in both groups (p<0.05). TH attenuated S90 plasma visfatin and, after rewarming, decreased R180 plasma IL-6, KC, and myoglobin (p<0.05) relative to NT. Heart and gut KC increased at S90 while IL-6 increases were delayed until R180 (p<0.05). NT produced sustained elevations of myocardial KC but decreased visfatin by R180, effects abrogated by TH (p<0.05).

CONCLUSIONS

In a mouse model of HS, TH improves hemodynamics and alters plasma and tissue proinflammatory cytokines including the novel cytokine visfatin. TH modulation of cytokines may attenuate cardiac dysfunction following HS.

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.

Core temperature correlates with expression of selected stress and immunomodulatory genes in febrile patients with sepsis and noninfectious SIRS

Environmental hyperthermia and exercise produce extensive changes in gene expression in human blood cells, but it is unknown whether this also happens during febrile-range hyperthermia. We tested the hypothesis that heat shock protein (HSP) and immunomodulatory stress gene expression correlate with fever in intensive care unit patients. Whole blood messenger RNA was obtained over consecutive days from 100 hospitalized patients suffering from sepsis or noninfectious systemic inflammatory response syndrome (SIRS) as defined by conventional criteria. The most abnormal body temperature in the preceding 24 h was recorded for each sample. Expression analysis was performed using the Affymetrix U133 chip. ANCOVA followed by correlation analysis was performed on a subset of 278 prospectively identified sequences of interest. Temperature affected expression of 60 sequences, either independently or as a function of clinical diagnosis. Forty-eight of these (representing 38 genes) were affected by temperature only, including several HSPs, transcription factors heat shock factor (HSF)-1 and HSF-4, cellular adhesion molecules such as ICAM1/CD54 and JAM3, toll receptors TLR-6 and TLR-7, ribosomal proteins, and a number of molecules involved in inflammatory pathways. Twelve sequences demonstrated temperature-dependent responses that differed significantly between patients with sepsis and noninfectious SIRS: CXCL-13; heat shock proteins DNAJB12 and DNAJC4; the F11 receptor; folate hydrolase 1; HSF-2; HSP 70 proteins HSPA1A, HSPA1B, and HSPA1L; interleukin 8; lipopolysaccharide binding protein; and prostaglandin E synthase. Febrile-range temperatures achieved during sepsis and noninfectious SIRS correlate with detectable changes in stress gene expression in vivo, suggesting that fever can activate HSP gene expression and modify innate immune responses. For some genes, it appears that clinical condition can alter temperature-sensitive gene expression. Collectively, these data underscore the potential importance of body temperature in shaping the immune response to infection and injury.

Hypothermia and surgery: immunologic mechanisms for current practice

OBJECTIVE

To examine cellular and immunologic mechanisms by which intraoperative hypothermia affects surgical patients.

SUMMARY BACKGROUND DATA

Avoidance of perioperative hypothermia has recently become a focus of attention as an important quality performance measure, aimed at optimizing the care of surgical patients. Anesthetized surgical patients are particularly at risk for hypothermia, which has been directly linked to the development of sequelae, such as coagulopathy, infection, morbid myocardial events, and death after surgery. However, many of the underlying immunologic mechanisms remain unclear.

METHODS

Venous blood samples from healthy volunteers were exposed for up to 4 hours to various temperatures following the addition of a 1 ng/mL lipopolysaccharide challenge. Innate immune function, assessed by the ability of monocytes to present antigen and coordinate cytokine release, was determined by qualitative and quantitative measurements of HLA-DR surface expression 2 hours following incubation, and proinflammatory tumor necrosis factor-alpha (TNF-alpha) and anti-inflammatory (IL-10) cytokine release in the first 4 hours.

RESULTS

Monocyte incubation at hypothermic temperatures (34 degrees C) reduced HLA-DR surface expression, delayed TNF-alpha clearance, and increased IL-10 release. Conversely, hyperthermia (40 degrees C) increased monocyte antigen presentation and resulted in rapid decay of TNF-alpha. However, IL-10 release was also increased. Normothermia (37 degrees C) attenuated IL-10 release following the initial proinflammatory surge.

CONCLUSION

Hypothermia exerts multiple effects at the cellular level, which impair innate immune function, and are associated with increased septic complications and mortality. These findings provide a physiological basis for perioperative temperature monitoring, which is a valid surgical performance measure that can be used to reduce surgical complications associated with avoidable hypothermia.

Mast cells are necessary for the hypothermic response to LPS-induced sepsis

As central nervous system residents, mast cells contain many cytokines and are localized primarily near large blood vessels in the diencephalon and within the leptomeninges, making them candidates for immune to neural "cross talk." Using mast cell-deficient Kit(W-sh/W-sh) mice, we assessed the role of these cells in the thermoregulatory component of the immune response to lipopolysaccharide (LPS). Kit(W-sh/W-sh) and wild-type (WT) mice differed in several respects in response to injection of a high dose of LPS (1 mg/kg ip). Core temperature (T(c)) of WT mice decreased by approximately 3 degrees C, whereas Kit(W-sh/W-sh) mice did not become hypothermic but instead exhibited pronounced low-frequency T(c) oscillations around their baseline temperature. In addition, Kit(W-sh/W-sh) mice had lower levels of whole brain TNF-alpha but no differences in IL-1beta, IL-6, IFN-gamma, or histamine compared with WT mice following injection of the high dose of LPS, consistent with the role of TNF-alpha in sepsis. Kit(W-sh/W-sh) mice had increased resistance to LPS, and some survived a dose of LPS that was lethal in littermate controls. In contrast, Kit(W-sh/W-sh) and WT mice were similar in other aspects, namely, in the hyperthermia following injection of TNF-alpha (1.5 microg icv), reduced nighttime T(c) and locomotor activity (to 1 mg/kg LPS), response to a low dose of LPS (10 microg/kg ip), and response to subcutaneous turpentine injection. These results indicate that mast cells play a role in the regulation of thermoregulatory responses and survival following sepsis induction and suggest a brain site of action.

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.