A subset of 26S proteasomes is activated at critically low ATP concentrations and contributes to myocardial injury during cold ischemia

Molecular mechanisms leading to myocardial injury during warm or cold ischemia are insufficiently understood. Although proteasomes are thought to contribute to myocardial ischemia-reperfusion injury, their roles during the ischemic period remain elusive. Because donor hearts are commonly exposed to prolonged global cold ischemia prior to cardiac transplantation, we evaluated the role and regulation of the proteasome during cold ischemic storage of rat hearts in context of the myocardial ATP content. When measured at the actual tissue ATP concentration, cardiac proteasome peptidase activity increased by 225% as ATP declined during cold ischemic storage of hearts in University of Wisconsin (UW) solution for up to 48 h. Addition of the specific proteasome inhibitor epoxomicin to the UW solution inhibited proteasome activity in the cardiac extracts, significantly reduced edema formation and preserved the ultrastructural integrity of the cardiomyocyte. Utilizing purified 20S/26S proteasome enzyme preparations, we demonstrate that this activation can be attributed to a subset of 26S proteasomes which are stable at ATP concentrations far below physiological levels, that ATP negatively regulates its activity and that maximal activation occurs at ATP concentrations in the low μmol/L range. These data suggest that proteasome activation is a pathophysiologically relevant mechanism of cold ischemic myocardial injury. A subset of 26S proteasomes appears to be a cell-destructive protease that is activated as ATP levels decline. Proteasome inhibition during cold ischemia preserves the ultrastructural integrity of the cardiomyocyte.     

Effect of induced mild hypothermia on two pro-inflammatory cytokines and oxidative parameters during experimental acute sepsis

Abstract

This study aimed to determine the effect of induced mild hypothermia (34°C) on the production of two cytokines (interleukin (IL-6) and tumor necrosis factor (TNF)alpha) and reactive nitrogen and oxygen species in plasma and the heart of acutely septic rats. After anesthesia and in conditions of normothermia (38°C) or mild hypothermia (34°C), acute sepsis was induced by cecal ligation and perforation. For each temperature three groups were formed: (1) baseline (blood sample collected at T0 hour), (2) sham (blood sample at T4 hours) and (3) septic (blood sample at T4 hours). At either temperature sepsis induced a significant increase in plasma IL-6, TNF-alpha and HO^? concentration, compared with the sham groups (P ≤ 0.016). Compared with the normothermic septic group, septic rats exposed to mild hypothermia showed a mild decrease in TNF-alpha concentration (104 ± 50 pg/ml vs. 215 ± 114 pg/ml; P > 0.05) and a significant decrease in IL-6 (1131 ± 402 pg/ml vs. 2494 ± 691 pg/ml, P = 0.038). At either temperature sepsis induced no enhancement within the heart of lipoperoxidation (malondialdehyde content) or antioxidant activities (superoxide dismutase and catalase). In conclusion, during acute sepsis, induced mild hypothermia appears to reduce some pro-inflammatory and oxidative responses. This may, in part, explain the beneficial effect of hypothermia on survival duration of septic rats.     

Intermittent Hypothermia Is Neuroprotective in an in vitro Model of Ischemic Stroke

Objective: To investigate whether the intermittent hypothermia (IH) protects neurons against ischemic insult and the potential molecular targets using an in vitro ischemic model of oxygen glucose deprivation (OGD).Methods: Fetal rat cortical neurons isolated from Day E18 rat embryos were subjected to 90-min OGD and hypothermia treatments during reoxygenation before examining the changes in microscopic morphology, cell viability, microtubule- associated protein 2 (MAP-2) release, intracellular pH value and calcium, reactive oxygen species (ROS) generation, mitochondrial membrane potential (△Ψm) and neuronal death using cell counting kit (CCK-8), enzyme-linked immunosorbent assay (ELISA), BCECF AM, Fluo-3 AM, DCFH-DA and dihydroethidium (DHE), JC-1 staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), respectively.Results: 90-min OGD induced morphologic abnormalities, cell viability decline, MAP-2 release, intracellular acidosis, calcium overload, increased ROS generation, △Ψm decrease and cell death in primary neurons, which was partially inhibited by continuous hypothermia (CH) and intermittent hypothermia (IH). Interestingly, 6-h CH was insufficient to reduce intracellular calcium overload and stabilize mitochondrial membrane potential (△Ψm), while 12-h CH was effective in reversing the above changes. All IH treatments (6×1 h, 4×1.5 h or 3×2 h) effectively attenuated intracellular free calcium overload, inhibited ROS production, stabilized mitochondrial membrane potential (△Ψm) and reduced delayed cell death in OGD-treated cells. However, only IH intervals longer than 1.5 h appeared to be effective in preventing cell viability loss and intracellular pH decline.Conclusion: Both CH and IH were neuroprotective in an in vitro model of ischemic stroke, and in spite of shorter hypothermia duration, IH could provide a comparable neuroprotection to CH.     

Schistosoma co-infection protects against brain pathology but does not prevent severe disease and death in a murine model of cerebral malaria

Co-infections of helminths and malaria parasites are common in human populations in most endemic areas. It has been suggested that concomitant helminth infections inhibit the control of malaria parasitemia but down-modulate severe malarial disease. We tested this hypothesis using a murine co-infection model of schistosomiasis and cerebral malaria. C57BL/6 mice were infected with Schistosoma mansoni and 8-9 weeks later, when Schistosoma infection was patent, mice were co-infected with Plasmodium berghei ANKA strain. We found that a concomitant Schistosoma infection increased parasitemia at the beginning of the P. berghei infection. It did not protect against P. berghei-induced weight loss and hypothermia, and P. berghei-mono-infected as well as S. mansoni-P. berghei-co-infected animals showed a high case fatality between days 6 and 8 of malarial infection. However, co-infection significantly reduced P. berghei-induced brain pathology. Over 40% of the S. mansoni-P. berghei-co-infected animals that died during this period were completely protected against haemorrhaging, plugging of blood vessels and infiltration, indicating that mortality in these animals was not related to cerebral disease. Schistosoma mansoni-P. berghei-co-infected mice had elevated plasma concentrations of IL-5 and IL-13 and on day 6 lower levels of IFN-γ, IL-10, monocyte chemoattractant protein-1 (MCP-1) and monokine induced by IFN-γ (MIG) than P. berghei-mono-infected mice. We conclude that in P. berghei infections, disease and early death are caused by distinct pathogenic mechanisms, which develop in parallel and are differentially influenced by the immune response to S. mansoni. This might explain why, in co-infected mice, death could be induced in the absence of brain pathology.     

The unfolded protein response in human corneal endothelial cells following hypothermic storage: implications of a novel stress pathway

Human corneal endothelial cells (HCEC) have become increasingly important for a range of eye disease treatment therapies. Accordingly, a more detailed understanding of the processing and preservation associated stresses experienced by corneal cells might contribute to improved therapeutic outcomes. To this end, the unfolded protein response (UPR) pathway was investigated as a potential mediator of corneal cell death in response to hypothermic storage. Once preservation-induced failure had begun in HCECs stored at 4 °C, it was noted that necrosis accounted for the majority of cell death but with significant apoptotic involvement, peaking at several hours post-storage (4–8 h). Western blot analysis demonstrated changes associated with apoptotic activation (caspase 9, caspase 3, and PARP cleavage). Further, the activation of the UPR pathway was observed through increased and sustained levels of ER folding and chaperone proteins (Bip, PDI, and ERO1-Lα) in samples experiencing significant cell death. Modulation of the UPR pathway using the specific inhibitor, salubrinal, resulted in a 2-fold increase in cell survival in samples experiencing profound cold-induced failure. Furthermore, this increased cell survival was associated with increased membrane integrity, cell attachment, and decreased necrotic cell death populations. Conversely, addition of the UPR inducer, tunicamycin, during cold exposure resulted in a significant decrease in HCEC survival during the recovery period. These data implicate for the first time that this novel cell stress pathway may be activated in HCEC as a result of the complex stresses associated with hypothermic exposure. The data suggest that the targeted control of the UPR pathway during both processing and preservation protocols may improve cell survival and function of HCEC thus improving the clinical utility of these cells as well as whole human corneas.     

The efficacy of pre-warming on reducing intraprocedural hypothermia in endovascular coiling of cerebral aneurysms

Background

The anesthetic management of patients undergoing endovascular treatment of cerebral aneurysms in the interventional neuroradiology suite can be challenged by hypothermia because of low ambient temperature for operating and maintaining its equipments. We evaluated the efficacy of skin surface warming prior to induction of anesthesia to prevent the decrease in core temperature and reduce the incidence of hypothermia.

Methods

Seventy-two patients were randomized to pre-warmed and control group. The patients in pre-warmed group were warmed 30 minutes before induction with a forced-air warming blanket set at 38°C. Pre-induction tympanic temperature (Tpre) was measured using an infrared tympanic thermometer and core temperature was measured at the esophagus immediately after intubation (T0) and recorded at 20 minutes intervals (T20, T40, T60, T80, T100, and T120). The number of patients who became hypothermic at each time was recorded.

Results

Tpre in the control and pre-warmed group were 36.4 ± 0.4°C and 36.6 ± 0.3°C, whereas T0 were 36.5 ± 0.4°C and 36.6 ± 0.2°C. Core temperatures in the pre-warmed group were significantly higher than the control group at T20, T40, T60, T80, T100, and T120 (P < 0.001). Compared to T0, core temperatures at each time were significantly lower in both two groups (P = 0.007 at T20 in pre-warmed group, P < 0.001 at the other times in both groups). The incidence of hypothermia was significantly lower in the pre-warmed group than the control group from T20 to T120 (P = 0.002 at T20, P < 0.001 at the other times).

Conclusion

Pre-warming for 30 minutes at 38°C did not modify the trends of the temperature decrease seen in the INR suite. It just slightly elevated the beginning post intubation base temperature. The rate of decrease was similar from T20 to T120. However, pre-warming considerably reduced the risk of intraprocedural hypothermia.

Trial registration

Clinical Research Information Service (CRiS) Identifier: KCT0001320. Registered December 19th, 2014.     

全身麻醉术后患者苏醒室内低体温发生率及其影响因素的Logistic回归分析

摘要 目的：统计全身麻醉术后患者苏醒室内低体温发生率,并分析其影响因素。方法：以2020年5月~2020年10月我院收治的110例接受全身麻醉手术的患者为研究对象,采用回顾性分析方法,整理患者的病历资料。观察全身麻醉术后患者苏醒室内低体温发生率,发生低体温的列为低体温组,未发生低体温的列为正常体温组,采用多因素Logistic回归分析低体温的相关因素。结果：全身麻醉术后患者苏醒室内低体温患者为15例,低体温发生率为13.64%（15/110）。单因素分析发现,全身麻醉术后患者苏醒室内低体温发生与年龄、麻醉时间、手术时间、美国麻醉医师协会（ASA）分级、苏醒延迟、术中输液量有关（P<0.05）,而与性别、体质量指数、术中环境温度、术前血红蛋白无关（P>0.05）。多因素Logistic回归分析结果显示,手术时间>4h、ASA分级为Ⅲ~Ⅳ级、术中输液量>1300 mL、年龄>60岁为全身麻醉术后患者苏醒室内低体温发生的影响因素（P<0.05）。结论：全身麻醉术后患者苏醒室内低体温的发生不可避免,且受多种因素影响,需尽量缩短手术时间,做好输入液体保温,特别做好老年患者保温工作,以减少低体温的发生风险。     

Seasonal Rhythms of Body Temperature in the Free‐Ranging Raccoon Dog (Nyctereutes procyonoides) with Special Emphasis on Winter Sleep

The raccoon dog (Nyctereutes procyonoides) is the only canid with passive overwintering in areas with cold winters, but the depth and rhythmicity of wintertime hypothermia in the wild raccoon dog are unknown. To study the seasonal rhythms of body temperature (T_b), seven free‐ranging animals were captured and implanted with intra‐abdominal T_b loggers and radio‐tracked during years 2004–2006. The average size of the home ranges was 306±26 ha, and the average 24 h T_b was 38.0±<0.01°C during the snow‐free period (May–November). The highest and lowest T_b were usually recorded around midnight (21∶00–02∶00 h) and between 05∶00–11∶00 h, respectively, and the range of the 24 h oscillations was 1.2±0.01°C. The animals lost approximately 43±6% of body mass in winter (December–April), when the average size of the home ranges was 372±108 ha. During the 2–9‐wk periods of passivity in January–March, the average 24 h T_b decreased by 1.4–2.1°C compared to the snow‐free period. The raccoon dogs were hypothermic for 5 h in the morning (06∶00–11∶00 h), whereas the highest T_b values were recorded between 16∶00–23∶00 h. The range of the 24 h oscillations increased by approximately 0.6°C, and the rhythmicity was more pronounced than in the snow‐free period. The ambient temperature and depth of snow cover were important determinants of the seasonal T_b rhythms. The overwintering strategy of the raccoon dog resembled the patterns of winter sleep in bears and badgers, but the wintertime passivity of the species was more intermittent and the decrease in the T_b less pronounced.     

Influence of temperature on ischemic brain: basic and clinical principles

In the last decades, the interest in the association between body temperature and stroke outcome has reemerged, and the use of animal models has made it possible to know the underlying pathogenic mechanisms involved, most of them with pending confirmation in human clinics. In this work, we will review the effects of hyperthermia and hypothermia and its pathogenesis on ischemic stroke, and the evidence of the efficacy and safety of anti-hyperthermic and hypothermic treatments. We will describe how treatment of hyperthermia on ischemic stroke patients, improves patient comfort and outcome, both in the short and the long term, but new clinical studies are needed in this field. Despite the theoretical and experimental bases in favor of hypothermia for the treatment of brain ischemia, there is no definitive clinical evidence that has proved its benefits, so far. With current knowledge, an objective of a body temperature between 35.5 and 36.5 °C seems an optimal therapeutic target for both hyperthermic and normothermic patients.     

Body temperatures during three long-distance polar swims in water of 0–3 °C

1.

We report body temperature responses in a single individual to 3 swims of 1000 m or longer in ice-cold water (0–3 °C) during which he swam the normal crawl stroke with his face in the water whilst wearing only a swimming costume, swimming cap and goggles.