Biofilm exopolysaccharides alter sensory-neuron-mediated sickness during lung infection.

Infections of the lung cause observable sickness thought to be secondary to inflammation. Signs of sickness are crucial to alert others via behavioral-immune responses to limit contact with contagious individuals. Gram-negative bacteria produce exopolysaccharide (EPS) that provides microbial protection; however, the impact of EPS on sickness remains uncertain. Using genome-engineered Pseudomonas aeruginosa (P. aeruginosa) strains, we compared EPS-producers versus non-producers and a virulent Escherichia coli (E. coli) lung infection model in male and female mice. EPS-negative P. aeruginosa and virulent E. coli infection caused severe sickness, behavioral alterations, inflammation, and hypothermia mediated by TLR4 detection of the exposed lipopolysaccharide (LPS) in lung TRPV1+ sensory neurons. However, inflammation did not account for sickness. Stimulation of lung nociceptors induced acute stress responses in the paraventricular hypothalamic nuclei by activating corticotropin-releasing hormone neurons responsible for sickness behavior and hypothermia. Thus, EPS-producing biofilm pathogens evade initiating a lung-brain sensory neuronal response that results in sickness.

CLSTN3ß enforces adipocyte multilocularity to facilitate lipid utilization.

Multilocular adipocytes are a hallmark of thermogenic adipose tissue1,2, but the factors that enforce this cellular phenotype are largely unknown. Here, we show that an adipocyte-selective product of the Clstn3 locus (CLSTN3ß) present in only placental mammals facilitates the efficient use of stored triglyceride by limiting lipid droplet (LD) expansion. CLSTN3ß is an integral endoplasmic reticulum (ER) membrane protein that localizes to ER-LD contact sites through a conserved hairpin-like domain. Mice lacking CLSTN3ß have abnormal LD morphology and altered substrate use in brown adipose tissue, and are more susceptible to cold-induced hypothermia despite having no defect in adrenergic signalling. Conversely, forced expression of CLSTN3ß is sufficient to enforce a multilocular LD phenotype in cultured cells and adipose tissue. CLSTN3ß associates with cell death-inducing DFFA-like effector proteins and impairs their ability to transfer lipid between LDs, thereby restricting LD fusion and expansion. Functionally, increased LD surface area in CLSTN3ß-expressing adipocytes promotes engagement of the lipolytic machinery and facilitates fatty acid oxidation. In human fat, CLSTN3B is a selective marker of multilocular adipocytes. These findings define a molecular mechanism that regulates LD form and function to facilitate lipid utilization in thermogenic adipocytes.

Hypothermia or Machine Perfusion in Kidney Donors.

BACKGROUND: Therapeutic hypothermia in brain-dead organ donors has been shown to reduce delayed graft function in kidney recipients after transplantation. Data are needed on the effect of hypothermia as compared with machine perfusion on outcomes after kidney transplantation. METHODS: At six organ-procurement facilities in the United States, we randomly assigned brain-dead kidney donors to undergo therapeutic hypothermia (hypothermia group), ex situ kidney hypothermic machine perfusion (machine-perfusion group), or both (combination-therapy group). The primary outcome was delayed graft function in the kidney transplant recipients (defined as the initiation of dialysis during the first 7 days after transplantation). We also evaluated whether hypothermia alone was noninferior to machine perfusion alone and whether the combination of both methods was superior to each of the individual therapies. Secondary outcomes included graft survival at 1 year after transplantation. RESULTS: From 725 enrolled donors, 1349 kidneys were transplanted: 359 kidneys in the hypothermia group, 511 in the machine-perfusion group, and 479 in the combined-therapy group. Delayed graft function occurred in 109 patients (30%) in the hypothermia group, in 99 patients (19%) in the machine-perfusion group, and in 103 patients (22%) in the combination-therapy group. Adjusted risk ratios for delayed graft function were 1.72 (95% confidence interval [CI], 1.35 to 2.17) for hypothermia as compared with machine perfusion, 1.57 (95% CI, 1.26 to 1.96) for hypothermia as compared with combination therapy, and 1.09 (95% CI, 0.85 to 1.40) for combination therapy as compared with machine perfusion. At 1 year, the frequency of graft survival was similar in the three groups. A total of 10 adverse events were reported, including cardiovascular instability in 9 donors and organ loss in 1 donor owing to perfusion malfunction. CONCLUSIONS: Among brain-dead organ donors, therapeutic hypothermia was inferior to machine perfusion of the kidney in reducing delayed graft function after transplantation. The combination of hypothermia and machine perfusion did not provide additional protection. (Funded by Arnold Ventures; ClinicalTrials.gov number, NCT02525510.).

CTRP6 promotes the macrophage inflammatory response, and its deficiency attenuates LPS-induced inflammation.

Macrophages play critical roles in inflammation and tissue homeostasis, and their functions are regulated by various autocrine, paracrine, and endocrine factors. We have previously shown that CTRP6, a secreted protein of the C1q family, targets both adipocytes and macrophages to promote obesity-linked inflammation. However, the gene programs and signaling pathways directly regulated by CTRP6 in macrophages remain unknown. Here, we combine transcriptomic and phosphoproteomic analyses to show that CTRP6 activates inflammatory gene programs and signaling pathways in mouse bone marrow-derived macrophages (BMDMs). Treatment of BMDMs with CTRP6 upregulated proinflammatory, and suppressed the antiinflammatory, gene expression. We also showed that CTRP6 activates p44/42-MAPK, p38-MAPK, and NF-κB signaling pathways to promote inflammatory cytokine secretion from BMDMs, and that pharmacologic inhibition of these signaling pathways markedly attenuated the effects of CTRP6. Pretreatment of BMDMs with CTRP6 also sensitized and potentiated the BMDMs response to lipopolysaccharide (LPS)-induced inflammatory signaling and cytokine secretion. Consistent with the metabolic phenotype of proinflammatory macrophages, CTRP6 treatment induced a shift toward aerobic glycolysis and lactate production, reduced oxidative metabolism, and elevated mitochondrial reactive oxygen species production in BMDMs. Importantly, in accordance with our in vitro findings, BMDMs from CTRP6-deficient mice were less inflammatory at baseline and showed a marked suppression of LPS-induced inflammatory gene expression and cytokine secretion. Finally, loss of CTRP6 in mice also dampened LPS-induced inflammation and hypothermia. Collectively, our findings suggest that CTRP6 regulates and primes the macrophage response to inflammatory stimuli and thus may have a role in modulating tissue inflammatory tone in different physiological and disease contexts.

Cognitive Effects of Body Temperature During Hypothermic Circulatory Arrest Trial (GOT ICE): A Randomized Clinical Trial Comparing Outcomes After Aortic Arch Surgery.

BACKGROUND: Deep hypothermia has been the standard for hypothermic circulatory arrest (HCA) during aortic arch surgery. However, centers worldwide have shifted toward lesser hypothermia with antegrade cerebral perfusion. This has been supported by retrospective data, but there has yet to be a multicenter, prospective randomized study comparing deep versus moderate hypothermia during HCA. METHODS: This was a randomized single-blind trial (GOT ICE [Cognitive Effects of Body Temperature During Hypothermic Circulatory Arrest]) of patients undergoing arch surgery with HCA plus antegrade cerebral perfusion at 4 US referral aortic centers (August 2016-December 2021). Patients were randomized to 1 of 3 hypothermia groups: DP, deep (≤20.0 °C); LM, low-moderate (20.1-24.0 °C); and HM, high-moderate (24.1-28.0 °C). The primary outcome was composite global cognitive change score between baseline and 4 weeks postoperatively. Analysis followed the intention-to-treat principle to evaluate if: (1) LM noninferior to DP on global cognitive change score; (2) DP superior to HM. The secondary outcomes were domain-specific cognitive change scores, neuroimaging findings, quality of life, and adverse events. RESULTS: A total of 308 patients consented; 282 met inclusion and were randomized. A total of 273 completed surgery, and 251 completed the 4-week follow-up (DP, 85 [34%]; LM, 80 [34%]; HM, 86 [34%]). Mean global cognitive change score from baseline to 4 weeks in the LM group was noninferior to the DP group; likewise, no significant difference was observed between DP and HM. Noninferiority of LM versus DP, and lack of difference between DP and HM, remained for domain-specific cognitive change scores, except structured verbal memory, with noninferiority of LM versus DP not established and structured verbal memory better preserved in DP versus HM (P = 0.036). There were no significant differences in structural or functional magnetic resonance imaging brain imaging between groups postoperatively. Regardless of temperature, patients who underwent HCA demonstrated significant reductions in cerebral gray matter volume, cortical thickness, and regional brain functional connectivity. Thirty-day in-hospital mortality, major morbidity, and quality of life were not different between groups. CONCLUSIONS: This randomized multicenter study evaluating arch surgery HCA temperature strategies found low-moderate hypothermia noninferior to traditional deep hypothermia on global cognitive change 4 weeks after surgery, although in secondary analysis, structured verbal memory was better preserved in the deep group. The verbal memory differences in the low- and high-moderate groups and structural and functional connectivity reductions from baseline merit further investigation and suggest opportunities to further optimize brain perfusion during HCA. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02834065.

The Protective Effect and Mechanism of Mild Hypothermia on Lung Injury after Cardiopulmonary Resuscitation in Pigs.

To explore the protective effect and mechanism of mild hypothermia on lung tissue damage after cardiopulmonary resuscitation in pigs. In this experiment, we electrically stimulated 16 pigs (30 ± 2 kg) for 10 min to cause ventricular fibrillation. The successfully resuscitated animals were randomly divided into two groups, a mild hypothermia group and a control group. We took arterial blood 0.5, 1, 3, and 6 h after ROSC recovery in the two groups of animals for blood gas analysis. We observed the structural changes of lung tissue under an electron microscope and calculate the wet weight/dry weight (W/D) ratio. We quantitatively analyzed the expression differences of representative inflammatory factors [interleukin-6 (IL-6) and tumor necrosis factor-alpha TNF-α)] through the ELISA test. We detected the expression levels of Bax, Bcl-2, and Caspase-3 proteins in lung tissues by Western blot. After 3 h and 6 h of spontaneous circulation was restored, compared with the control group, PaO2/FiO2 decreased significantly (P < 0.05). In addition, the pathological changes, lung W/D and lung MDA of the mild hypothermia group were better than those of the control group. The levels of IL-6 and TNF-α in the lung tissue of the mild hypothermia group were significantly lower than those of the control group (P < 0.05). The content of Caspase-3 and Bax in the mild hypothermia group was significantly lower than that of the control group. Our experiments have shown that mild hypothermia can reduce lung tissue damage after cardiopulmonary resuscitation.

Seizures Cause Prolonged Impairment of Ventilation, CO2 Chemoreception and Thermoregulation.

Sudden unexpected death in epilepsy (SUDEP) has been linked to respiratory dysfunction, but the mechanisms underlying this association remain unclear. Here we found that both focal and generalized convulsive seizures (GCSs) in epilepsy patients caused a prolonged decrease in the hypercapnic ventilatory response (HCVR; a measure of respiratory CO2 chemoreception). We then studied Scn1a R1407X/+ (Dravet syndrome; DS) and Scn8a N1768D/+ (D/+) mice of both sexes, two models of SUDEP, and found that convulsive seizures caused a postictal decrease in ventilation and severely depressed the HCVR in a subset of animals. Those mice with severe postictal depression of the HCVR also exhibited transient postictal hypothermia. A combination of blunted HCVR and abnormal thermoregulation is known to occur with dysfunction of the serotonin (5-hydroxytryptamine; 5-HT) system in mice. Depleting 5-HT with para-chlorophenylalanine (PCPA) mimicked seizure-induced hypoventilation, partially occluded the postictal decrease in the HCVR, exacerbated hypothermia, and increased postictal mortality in DS mice. Conversely, pretreatment with the 5-HT agonist fenfluramine reduced postictal inhibition of the HCVR and hypothermia. These results are consistent with the previous observation that seizures cause transient impairment of serotonergic neuron function, which would be expected to inhibit the many aspects of respiratory control dependent on 5-HT, including baseline ventilation and the HCVR. These results provide a scientific rationale to investigate the interictal and/or postictal HCVR as noninvasive biomarkers for those at high risk of seizure-induced death, and to prevent SUDEP by enhancing postictal 5-HT tone.SIGNIFICANCE STATEMENT There is increasing evidence that seizure-induced respiratory dysfunction contributes to the pathophysiology of sudden unexpected death in epilepsy (SUDEP). However, the cellular basis of this dysfunction has not been defined. Here, we show that seizures impair CO2 chemoreception in some epilepsy patients. In two mouse models of SUDEP we found that generalized convulsive seizures impaired CO2 chemoreception, and induced hypothermia, two effects reported with serotonergic neuron dysfunction. The defects in chemoreception and thermoregulation were exacerbated by chemical depletion of serotonin and reduced with fenfluramine, suggesting that seizure-induced respiratory dysfunction may be due to impairment of serotonin neuron function. These findings suggest that impaired chemoreception because of transient inhibition of serotonergic neurons may contribute to the pathophysiology of SUDEP.

Cold-induced chromatin compaction and nuclear retention of clock mRNAs resets the circadian rhythm.

Cooling patients to sub-physiological temperatures is an integral part of modern medicine. We show that cold exposure induces temperature-specific changes to the higher-order chromatin and gene expression profiles of human cells. These changes are particularly dramatic at 18°C, a temperature synonymous with that experienced by patients undergoing controlled deep hypothermia during surgery. Cells exposed to 18°C exhibit largely nuclear-restricted transcriptome changes. These include the nuclear accumulation of mRNAs encoding components of the negative limbs of the core circadian clock, most notably REV-ERBα. This response is accompanied by compaction of higher-order chromatin and hindrance of mRNPs from engaging nuclear pores. Rewarming reverses chromatin compaction and releases the transcripts into the cytoplasm, triggering a pulse of negative limb gene proteins that reset the circadian clock. We show that cold-induced upregulation of REV-ERBα is sufficient to trigger this reset. Our findings uncover principles of the cellular cold response that must be considered for current and future applications involving therapeutic deep hypothermia.

Mild hypothermia reduces lipopolysaccharide-induced microglial activation via down-regulation of Tent5c.

Microglial activation is a critical factor in the pathogenesis and progression of neuroinflammatory diseases. Mild hypothermia, known for its neuroprotective properties, has been shown to alleviate microglial activation. In this study, we explore the differentially expressed (DE) mRNAs and long non-coding RNAs (lncRNAs) in BV-2 microglial cells under different conditions: normal temperature (CN), mild hypothermia (YT), normal temperature with lipopolysaccharide (LPS), and mild hypothermia with LPS (LPS + YT). Venn analysis revealed 119 DE mRNAs that were down-regulated in the LPS + YT vs LPS comparison but up-regulated in the CN vs LPS comparison, primarily enriched in Gene Ontology terms related to immune and inflammatory responses. Furthermore, through Venn analysis of YT vs CN and LPS + YT vs LPS comparisons, we identified 178 DE mRNAs and 432 DE lncRNAs. Among these transcripts, we validated the expression of Tent5c at the protein and mRNA levels. Additionally, siRNA-knockdown of Tent5c attenuated the expression of pro-inflammatory genes (TNF-α, IL-1ß, Agrn, and Fpr2), cellular morphological changes, NLRP3 and p-P65 protein levels, immunofluorescence staining of p-P65 and number of cells with ASC-speck induced by LPS. Furthermore, Tent5c overexpression further potentiated the aforementioned indicators in the context of mild hypothermia with LPS treatment. Collectively, our findings highlight the significant role of Tent5c down-regulation in mediating the anti-inflammatory effects of mild hypothermia.

Hypothermia Treatment after Hypoxia-Ischemia in Glutathione Peroxidase-1 Overexpressing Mice.

The developing brain is uniquely susceptible to oxidative stress, and endogenous antioxidant mechanisms are not sufficient to prevent injury from a hypoxic-ischemic challenge. Glutathione peroxidase (GPX1) activity reduces hypoxic-ischemic injury. Therapeutic hypothermia (HT) also reduces hypoxic-ischemic injury, in the rodent and the human brain, but the benefit is limited. Here, we combined GPX1 overexpression with HT in a P9 mouse model of hypoxia-ischemia (HI) to test the effectiveness of both treatments together. Histological analysis showed that wild-type (WT) mice with HT were less injured than WT with normothermia. In the GPX1-tg mice, however, despite a lower median score in the HT-treated mice, there was no significant difference between HT and normothermia. GPX1 protein expression was higher in the cortex of all transgenic groups at 30 min and 24 h, as well as in WT 30 min after HI, with and without HT. GPX1 was higher in the hippocampus of all transgenic groups and WT with HI and normothermia, at 24 h, but not at 30 min. Spectrin 150 was higher in all groups with HI, while spectrin 120 was higher in HI groups only at 24 h. There was reduced ERK1/2 activation in both WT and GPX1-tg HI at 30 min. Thus, with a relatively moderate insult, we see a benefit with cooling in the WT but not the GPX1-tg mouse brain. The fact that we see no benefit with increased GPx1 here in the P9 model (unlike in the P7 model) may indicate that oxidative stress in these older mice is elevated to an extent that increased GPx1 is insufficient for reducing injury. The lack of benefit of overexpressing GPX1 in conjunction with HT after HI indicates that pathways triggered by GPX1 overexpression may interfere with the neuroprotective mechanisms provided by HT.

Synergistic effect of sildenafil combined with controlled hypothermia to alleviate microglial activation after neonatal hypoxia-ischemia in rats.

BACKGROUND AND PURPOSE: The only validated treatment to prevent brain damage associated with hypoxia-ischemia (HI) encephalopathy of the newborn is controlled hypothermia with limited benefits. Additional putative neuroprotective drug candidates include sildenafil citrate, a phosphodiesterase-type 5 inhibitor. The main objective of this preclinical study is to assess its ability to reduce HI-induced neuroinflammation, in particular through its potential effect on microglial activation. METHODS: HI was induced in P10 Sprague-Dawley rats by unilateral carotid permanent artery occlusion and hypoxia (HI) and treated by either hypothermia (HT) alone, Sildenafil (Sild) alone or combined treatment (SildHT). Lesion size and glial activation were analyzed by immunohistochemistry, qRT-PCR, and proteomic analyses performed at P13. RESULTS: None of the treatments was associated with a significant early reduction in lesion size 72h after HI, despite significant changes in tissue loss distribution. Significant reductions in both Iba1 + (within the ipsilateral hemisphere) and GFAP + cells (within the ipsilateral hippocampus) were observed in SildHT group, but not in the other treatment groups. In microglia-sorted cells, pro-inflammatory markers, i.e. Il1b, Il6, Nos2, and CD86 were significantly downregulated in SildHT treatment group only. These changes were restricted to the ipsilateral hemisphere, were not evidenced in sorted astrocytes, and were not sex dependent. Proteomic analyses in sorted microglia refined the pro-inflammatory effect of HI and confirmed a biologically relevant impact of SildHT on specific molecular pathways including genes related to neutrophilic functions. CONCLUSIONS: Our findings suggest that Sildenafil combined with controlled hypothermia produces maximum effect in mitigating microglial activation induced by HI through complex proteomic regulation. The reduction of neuroinflammation induced by Sildenafil may represent an interesting therapeutic strategy for neonatal neuroprotection.

Combined effects of mild hypothermia and nitrous-oxide-induced narcosis on manual and cognitive performance.

Divers are at enhanced risk of suffering from acute cognitive deterioration because of the low ambient temperatures and the narcotic action of inert gases inspired at high pressures. Yet, the behavioral effects of cold and inert gas narcosis have commonly been assessed in isolation and during short-term provocations. We therefore evaluated the interactive influence of mild hypothermia and narcosis engendered by a subanesthetic dose of nitrous oxide (N2O; a normobaric intervention analog of hyperbaric nitrogen) on cognitive function during prolonged iterative exposure. Fourteen men partook in two ∼12-h sessions (separated by ≥4 days), wherein they performed sequentially three 120-min cold (20°C) water immersions (CWIs), while inhaling, in a single-blinded manner, either normal air or a normoxic gas mixture containing 30% N2O. CWIs were separated by a 120-min rewarming in room-air breathing conditions. Before the first CWI and during each CWI, subjects performed a finger dexterity test, and the Spaceflight Cognitive Assessment Tool for Windows (WinSCAT) test assessing aspects of attention, memory, learning, and visuospatial ability. Rectal and skin temperatures were, on average, reduced by ∼1.2 °C and ∼8 °C, respectively (P < 0.001). Cooling per se impaired (P ≤ 0.01) only short-term memory (∼37%) and learning (∼18%); the impairments were limited to the first CWI. N2O also attenuated (P ≤ 0.02) short-term memory (∼37%) and learning (∼35%), but the reductions occurred in all CWIs. Furthermore, N2O invariably compromised finger dexterity, attention, concentration, working memory, and spatial processing (P < 0.05). The present results demonstrate that inert gas narcosis aggravates, in a persistent manner, basic and higher-order cognitive abilities during protracted cold exposure.

An untargeted metabolomics approach to study changes of the medium during human cornea culture.

INTRODUCTION: Two main approaches (organ culture and hypothermia) for the preservation and storage of human donor corneas are globally adopted for corneal preservation before the transplant. Hypothermia is a hypothermic storage which slows down cellular metabolism while organ culture, a corneal culture performed at 28-37 °C, maintains an active corneal metabolism. Researchers, till now, have just studied the impact of organ culture on human cornea after manipulating and disrupting tissues. OBJECTIVES: The aim of the current work was to optimize an analytical procedure which can be useful for discovering biomarkers capable of predicting tissue health status. For the first time, this research proposed a preliminary metabolomics study on medium for organ culture without manipulating and disrupting the valuable human tissues which could be still used for transplantation. METHODS: In particular, the present research proposed a method for investigating changes in the medium, over a storage period of 20 days, in presence and absence of a human donor cornea. An untargeted metabolomics approach using UHPLC-QTOF was developed to deeply investigate the differences on metabolites and metabolic pathways and the influence of the presence of the cornea inside the medium. RESULTS: Differences in the expression of some compounds emerged from this preliminary metabolomics approach, in particular in medium maintained for 10 and 20 days in presence but also in the absence of cornea. A total of 173 metabolites have been annotated and 36 pathways were enriched by pathway analysis. CONCLUSION: The results revealed a valuable untargeted metabolomics approach which can be applied in organ culture metabolomics.

Plasticity of mitochondrial function safeguards phosphorylating respiration during in vitro simulation of rest-phase hypothermia.

Many animals downregulate body temperature to save energy when resting (rest-phase hypothermia). Small birds that winter at high latitudes have comparatively limited capacity for hypothermia and so pay large energy costs for thermoregulation during cold nights. Available evidence suggests this process is fueled by adenosine triphosphate (ATP)-dependent mechanisms. Most ATP is produced by oxidative phosphorylation in the mitochondria, but mitochondrial respiration may be lower during hypothermia because of the temperature dependence of biological processes. This can create conflict between increased organismal ATP demand and a lower mitochondrial capacity to provide it. We studied this in blood cell mitochondria of wild great tits (Parus major) by simulating rest-phase hypothermia via a 6°C reduction in assay temperature in vitro. The birds had spent the night preceding the experiment in thermoneutrality or in temperatures representing mild or very cold winter nights, but night temperatures never affected mitochondrial respiration. However, across temperature groups, endogenous respiration was 14% lower in hypothermia. This did not reflect general thermal suppression of mitochondrial function because phosphorylating respiration was unaffected by thermal state. Instead, hypothermia was associated with a threefold reduction of leak respiration, from 17% in normothermia to 4% in hypothermia. Thus, the coupling of total respiration to ATP production was 96% in hypothermia, compared to 83% in normothermia. Our study shows that the thermal insensitivity of phosphorylation combined with short-term plasticity of leak respiration may safeguard ATP production when endogenous respiration is suppressed. This casts new light on the process by which small birds endure harsh winter cold and warrants future tests across tissues in vivo.

Deficiency of long-chain acyl-CoA synthetase 4 leads to lipopolysaccharide-induced mortality in a mouse model of septic shock.

Long-chain acyl-CoA synthetase 4 (ACSL4) converts free highly unsaturated fatty acids (HUFAs) into their acyl-CoA esters and is important for HUFA utilization. HUFA-containing phospholipids produced via ACSL4-dependent reactions are involved in pathophysiological events such as inflammatory responses and ferroptosis as a source for lipid mediators and/or a target of oxidative stress, respectively. However, the in vivo role of ACSL4 in inflammatory responses is not fully understood. This study sought to define the effects of ACSL4 deficiency on lipopolysaccharide (LPS)-induced systemic inflammatory responses using global Acsl4 knockout (Acsl4 KO) mice. Intraperitoneal injection of LPS-induced more severe symptoms, including diarrhea, hypothermia, and higher mortality, in Acsl4 KO mice within 24 h compared with symptoms in wild-type (WT) mice. Intestinal permeability induced 3 h after LPS challenge was also enhanced in Acsl4 KO mice compared with that in WT mice. In addition, plasma levels of some eicosanoids in Acsl4 KO mice 6 h post-LPS injection were 2- to 9-fold higher than those in WT mice. The increased mortality observed in LPS-treated Acsl4 KO mice was significantly improved by treatment with the general cyclooxygenase inhibitor indomethacin with a partial reduction in the severity of illness index for hypothermia, diarrhea score, and intestinal permeability. These results suggest that ACSL4 deficiency enhances susceptibility to endotoxin at least partly through the overproduction of cyclooxygenase-derived eicosanoids.

Hypothermia Attenuates Neurotoxic Microglial Activation via TRPV4.

Therapeutic hypothermia (TH) provides neuroprotection. However, the cellular mechanisms underlying the neuroprotective effects of TH are not fully elucidated. Regulation of microglial activation has the potential to treat a variety of nervous system diseases. Transient receptor potential vanilloid 4 (TRPV4), a nonselective cation channel, is activated by temperature stimulus at 27-35 °C. Although it is speculated that TRPV4 is associated with the neuroprotective mechanisms of TH, the role of TRPV4 in the neuroprotective effects of TH is not well understood. In the present study, we investigated whether hypothermia attenuates microglial activation via TRPV4 channels. Cultured microglia were incubated under normothermic (37 °C) or hypothermic (33.5 °C) conditions following lipopolysaccharide (LPS) stimulation. Hypothermic conditions suppressed the expression of pro-inflammatory cytokines, inducible nitric oxide synthase, and the number of phagocytic microglia. AMP-activated protein kinase (AMPK)-NF-κB signaling was inhibited under hypothermic conditions. Furthermore, hypothermia reduced neuronal damage induced by LPS-treated microglial cells. Treatment with TRPV4 antagonist in normothermic culture replicated the suppressive effects of hypothermia on microglial activation and microglia-induced neuronal damage. In contrast, treatment with a TRPV4 agonist in hypothermic culture reversed the suppressive effect of hypothermia. These findings suggest that TH suppresses microglial activation and microglia-induced neuronal damage via the TRPV4-AMPK-NF-κB pathway. Although more validation is needed to consider differences according to age, sex, and specific central nervous system regions, our findings may offer a novel therapeutic approach to complement TH.

A multi-center study to predict the risk of intraoperative hypothermia in gynecological surgery patients using preoperative variables.

OBJECTIVES: Hypothermia is highly common in patients undergoing gynecological surgeries under general anesthesia, so the length of hospitalization and even the risk of mortality are substantially increased. Our aim was to develop a simple and practical model to preoperatively identify gynecological surgery patients at risk of intraoperative hypothermia. METHODS: In this retrospective study, we collected data from 802 patients who underwent gynecological surgery at three medical centers from June 2022 to August 2023. We further allocated the patients to a training group, an internal validation group, or an external validation group. The preliminary predictive factors for intraoperative hypothermia in gynecological patients were determined using the least absolute shrinkage and selection operator (LASSO) method. The final predictive factors were subsequently identified through multivariate logistic regression analysis, and a nomogram for predicting the occurrence of hypothermia was established. RESULTS: A total of 802 patients were included, with 314 patients in the training cohort (mean age 48.5 ± 12.6 years), 130 patients in the internal validation cohort (mean age 49.9 ± 12.5 years), and 358 patients in the external validation cohort (mean age 47.6 ± 14.0 years). LASSO regression and multivariate logistic regression analyses indicated that body mass index, minimally invasive surgery, baseline heart rate, baseline body temperature, history of previous surgery, and aspartate aminotransferase level were associated with intraoperative hypothermia in gynecological surgery patients. This nomogram was constructed based on these six variables, with a C-index of 0.712 for the training cohort. CONCLUSIONS: We established a practical predictive model that can be used to preoperatively predict the occurrence of hypothermia in gynecological surgery patients. CLINICAL TRIAL REGISTRATION: chictr.org.cn, identifier ChiCTR2300071859.

Thermoregulation for very preterm infants in the delivery room: a narrative review.

Abnormal temperature in preterm infants is associated with increased morbidity and mortality. Infants born prematurely are at risk of abnormal temperature immediately after birth in the delivery room (DR). The World Health Organization (WHO) recommends that the temperature of newly born infants is maintained between 36.5-37.5oC after birth. When caring for very preterm infants, the International Liaison Committee on Resuscitation (ILCOR) recommends using a combination of interventions to prevent heat loss. While hypothermia remains prevalent, efforts to prevent it have increased the incidence of hyperthermia, which may also be harmful. Delayed cord clamping (DCC) for preterm infants has been recommended by ILCOR since 2015. Little is known about the effect of timing of DCC on temperature, nor have there been specific recommendations for thermal care before DCC. This review article focuses on the current evidence and recommendations for thermal care in the DR, and considers thermoregulation in the context of emerging interventions and future research directions. IMPACT: Abnormal temperature is common amongst very preterm infants after birth, and is an independent risk factor for mortality. The current guidelines recommend a combination of interventions to prevent heat loss after birth. Despite this, abnormal temperature is still a problem, across all climates and economies. New and emerging delivery room practice (i.e., delayed cord clamping, mobile resuscitation trolleys, early skin to skin care) may have an effect on infant temperature. This article reviews the current evidence and recommendations, and considers future research directions.

Therapeutic hypothermia modulates the neurogenic response of the newborn piglet subventricular zone after hypoxia-ischemia.

BACKGROUND: Neuroprotection combined with neuroregeneration may be critical for optimizing functional recovery in neonatal encephalopathy. To investigate the neurogenic response to hypoxia-ischemia (HI) followed by normothermia (38.5 °C) or three different hypothermic temperatures (35, 33.5, or 30 °C) in the subventricular zone (SVZ) of the neonatal piglet. METHODS: Following transient cerebral HI and resuscitation, 28 newborn piglets were randomized to: normothermia or whole-body cooling to 35 °C, 33.5 °C, or 30 °C during 2-26 h (all n = 7). At 48 h, piglets were euthanized and SVZ obtained to evaluate its cellularity, pattern of cell death, radial glia length, doublecortin (DCX, neuroblasts) expression, and Ki67 (cell proliferation) and Ki67/Sox2 (neural stem/progenitor dividing) cell counts. RESULTS: Normothermic piglets showed lower total (Ki67+) and neural stem/progenitor dividing (Ki67+Sox2+) cell counts when compared to hypothermic groups. Cooling to 33.5 °C obtained the highest values of SVZ cellularity, radial glia length processes, neuroblast chains area and DCX immunohistochemistry. Cooling to 30 °C, however, revealed decreased cellularity in the lateral SVZ and shorter radial glia processes when compared with 33.5 °C. CONCLUSIONS: In a neonatal piglet model, hypothermia to 33.5 °C modulates the neurogenic response of the SVZ after HI, highlighting the potential beneficial effect of hypothermia to 33.5 °C on endogenous neurogenesis and the detrimental effect of overcooling beyond this threshold. IMPACT: Neuroprotection combined with neuroregeneration may be critical for optimizing functional recovery in neonatal encephalopathy. Hypothermia may modulate neurogenesis in the subventricular zone (SVZ) of the neonatal hypoxic-ischemic piglet. Cooling to 33.5 °C obtained the highest values of SVZ cellularity, radial glia length processes, neuroblast chains area and doublecortin immunohistochemistry; cooling to 30 °C, however, revealed decreased cellularity and shorter radial glia processes. In a neonatal piglet model, therapeutic hypothermia (33.5 °C) modulates the neurogenic response of the SVZ after hypoxia-ischemia, highlighting also the detrimental effect of overcooling beyond this threshold.

Temperature probe placement in very preterm infants during delivery room stabilization: an open-label randomized trial.

BACKGROUND: Variation in practice exists for temperature probe positioning during stabilization of very preterm infants (<32 weeks gestation). We explored the influence of temperature probe sites on thermoregulation. METHODS: An open-label, stratified, balanced, parallel, randomized trial was conducted. Inborn infants were randomly assigned temperature probe to the axilla or to the upper back. The primary outcome was normothermia (local range: 36.8-37.3 °C and World Health Organization (WHO) range: 36.5-37.5 °C) at admission to the neonatal intensive care unit. RESULTS: Between 1 November 2018 and 4 July 2022, 178 infants were randomly assigned to one of the two sites (n = 89 each), 175 included in the final analysis. Normothermia (local range) was achieved for 39/87 infants (44.8%) assigned to the upper back compared to 28/88 infants (31.8%) assigned to the axilla [risk difference:13%; 95% CI -1.3-27.3]. Normothermia (WHO range) was achieved for 78/87 infants (89.7%) assigned to the upper back compared to 70/88 infants (79.6%) assigned to the axilla [risk difference:10.1%; 95% CI -0.5-20.7]. No infant recorded temperatures >38 °C or developed skin injury. CONCLUSIONS: In very preterm infants, upper back site was equally effective as the axilla in maintaining normothermia, with no increase in adverse events. CLINICAL TRIAL REGISTRATION: The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12620000293965). IMPACT: Substantial variation in practice exists for the site of securing a temperature probe during delivery room stabilization of very preterm infants and the influence of temperature probe site on thermoregulation remains unknown. In this study, upper back site was equally effective as the axilla in maintaining normothermia, with no increase in adverse events. Clinicians could adopt upper back site for maintaining normothermia. This study may contribute data to future international participant data prospective meta analysis of randomized controlled trials worldwide on temperature probe positioning in very preterm infants, increasing translation of research findings to optimize thermoregulation and clinical outcomes.