Hypothermia attenuates ischemia/reperfusion-induced endothelial cell apoptosis via alterations in apoptotic pathways and JNK signaling

Mild hypothermia pretreatment improves hepatic ischemia-reperfusion injury: A systematic review and meta-analysis of animal experiments

BACKGROUND AND AIM

Mild hypothermia in hepatic ischemia-reperfusion injury is increasingly being studied. This study aimed to conduct a systematic evaluation of the effectiveness of mild hypothermia in improving hepatic ischemia-reperfusion injury.

METHODS

We systematically searched CNKI, WanFang Data, PubMed, Embase, and Web of Science for original studies that used animal experiments to determine how mild hypothermia(32-34°C) pretreatment improves hepatic ischemia-reperfusion injury(in situ 70% liver IR model). The search period ranged from the inception of the databases to May 5, 2023. Two researchers independently filtered the literature, extracted the data, and assessed the risk of bias incorporated into the study. The meta-analysis was performed using RevMan 5.4.1 and Stata 15 software.

RESULTS

Eight randomized controlled trials (RCTs) involving a total of 117 rats/mice were included. The results showed that the ALT levels in the mild hypothermia pretreatment group were significantly lower than those in the normothermic control group [Standardized Mean Difference (SMD) = -5.94, 95% CI(-8.09, -3.78), P<0.001], and AST levels in the mild hypothermia pretreatment group were significantly lower than those in the normothermic control group [SMD = -4.45, 95% CI (-6.10, -2.78), P<0.001]. The hepatocyte apoptosis rate in the mild hypothermia pretreatment group was significantly lower than that in the normothermic control group [SMD = -6.86, 95% CI (-10.38, -3.33), P<0.001]. Hepatocyte pathology score in the mild hypothermia pretreatment group was significantly lower than that in the normothermic control group [SMD = -4.36, 95% CI (-5.78, -2.95), P<0.001]. There was no significant difference in MPO levels between the mild hypothermia preconditioning group and the normothermic control group [SMD = -4.83, 95% CI (-11.26, 1.60), P = 0.14]. SOD levels in the mild hypothermia preconditioning group were significantly higher than those in the normothermic control group [SMD = 3.21, 95% CI (1.27, 5.14), P = 0.001]. MDA levels in the mild hypothermia pretreatment group were significantly lower than those in the normothermic control group [SMD = -4.06, 95% CI (-7.06, -1.07) P = 0.008].

CONCLUSION

Mild hypothermia can attenuate hepatic ischemia-reperfusion injury, effectively reduce oxidative stress and inflammatory response, prevent hepatocyte apoptosis, and protect liver function.

The combination treatment of hypothermia and intranasal insulin ameliorates the structural and functional changes in a rat model of traumatic brain injury

The present study aimed to investigate the combination effects of hypothermia (HT) and intranasal insulin (INS) on structural changes of the hippocampus and cognitive impairments in the traumatic brain injury (TBI) rat model. The rats were divided randomly into the following five groups (n = 10): Sham, TBI, TBI with HT treatment for 3 h (TBI + HT), TBI with INS (ten microliters of insulin) treatment daily for 7 days (TBI + INS), and TBI with combining HT and INS (TBI + HT + INS). At the end of the 7th day, the open field and the Morris water maze tests were done for evaluation of anxiety-like behavior and memory performance. Then, after sacrificing, the brain was removed for stereological study. TBI led to an increase in the total volume of hippocampal subfields CA1 and DG and a decrease in the total number of neurons and non-neuronal cells in both sub-regions, which was associated with anxiety-like behavior and memory impairment. Although, the combination of HT and INS prevented the increased hippocampal volume and cell loss and improved behavioral performances in the TBI group. Our study suggests that the combined treatment of HT and INS could prevent increased hippocampal volume and cell loss in CA1 and DG sub-regions and consequently improve anxiety-like behaviors and memory impairment following TBI.

Autophagy Behavior under Local Hypothermia in Myocardiocytes Injury

Hypothermia and autophagy are critical regulators of cell homeostasis by regulating intra and intercellular cell communication. Myocardiocyte cryotherapy poses multiple cellular and subcellular effects on the injured cell, including upregulation of autophagy. Autophagy plays a crucial role in modifying cell metabolism by regulating downregulation, reducing reactive oxygen species production, and improving the natural cellular antioxidant defense system. Reduction of reactive oxygen species production and improving natural cellular antioxidant defense system. Therapeutic hypothermia ranges from 32-34°C in terms of local myocardiocyte cooling. Hypothermia induces autophagy by phosphorylating the Akt signaling pathway. Hypothermia has a more therapeutic effect when applied at the beginning of reperfusion rather than in the beginning of ischemia. Moderate hypothermia with 33°C poses most therapeutic effect by viability maintaining and reduction of reactive oxygen species release. Application of local hypothermia to myocardiocytes can be applied to infarcted myocardiocytes, anginal and to the cardiomyopathies.

Irisin inhibits NLRP3 inflammasome activation in HG/HF incubated cardiac microvascular endothelial cells with H/R injury

PURPOSE

NLRP3 inflammasome mediates myocardial ischemia/reperfusion (MI/R) injury and diabetic vascular endothelia dysfunction. However, the role of NLRP3 inflammasome in MI/R injury with diabetes has not been fully described. Irisin plays an important role in anti-inflammation and improves endothelial function in type 2 diabetes. The current study aimed to investigate the effect of irisin on regulating NLRP3 inflammasome activation in diabetic vascular endothelia dysfunction.

METHODS

Cardiac microvascular endothelial cells (CMECs) were cultured and subjected to high glucose/high fat (HG/HF) receiving hypoxia/reoxygenation (H/R) with irisin incubation or not. Then, apoptosis, viability, migration, NO secretion, and inflammasome activation were examined.

RESULTS

The hypoxic CMECs exhibited increased apoptosis, impaired viability, and migration, even decreased NO secretion and enhanced inflammasome activation. Moreover, irisin incubation decreased NLRP3 activation and attenuated cell injury in HG/HF cultured CMECs subjected to H/R injury, which was abolished by NLRP3 inflammasome activation. Meanwhile, NLRP3 inflammasome siRNA also attenuated H/R injury in CMECs under HG/HF condition.

CONCLUSION

The current study demonstrated for the first time that irisin inhibits NLRP3 inflammasome activation in CMECs as a novel mechanism in myocardial ischemia/reperfusion injury in diabetes.

Mild hypothermia ameliorates hepatic ischemia reperfusion injury by inducing RBM3 expression

Liver ischemia reperfusion injury (IRI) is a serious complication of certain liver surgeries, and it is difficult to prevent. As a potential drug-free treatment, mild hypothermia has been shown to promote positive outcomes in patients with IRI. However, the protective mechanism remains unclear. We established in vivo and in vitro models of hepatic ischemia reperfusion (IR) and mild hypothermia pretreatment. Hepatocytes were transfected with RNA-binding motif protein 3 (RBM3) overexpression plasmids, and IR was performed. Cell, culture medium, blood and tissue samples were collected to assess hepatic injury, oxidative stress, apoptosis and changes in RBM3 expression in the liver. Upregulation of RBM3 expression by mild hypothermia reduced the aminotransferase release, liver tissue injury and mitochondrial injury induced by liver IR. Hepatic IR-induced p38 and c-Jun N-terminal kinase (JNK) signaling pathway activation, oxidative stress injury and apoptosis could be greatly reversed by mild hypothermia. Overexpression of RBM3 mimicked the hepatoprotective effect of mild hypothermia. Mild hypothermia protects the liver from ischemia reperfusion-induced p38 and JNK signaling pathway activation, oxidative stress injury and apoptosis through the upregulation of RBM3 expression.

Effects of Different Hypothermia on the Results of Cardiopulmonary Resuscitation in a Cardiac Arrest Rat Model

Objective

To investigate the optimal temperature of hypothermia treatment in rats with cardiac arrest caused by ventricular fibrillation (VF) after the return of spontaneous circulation (ROSC).

Methods

A total of forty-eight male Sprague-Dawley rats were induced by VF through the guidewire with a maximum of 5 mA current and untreated for 8 min. Cardiopulmonary resuscitation (CPR) was performed for 8 min followed by defibrillation (DF). Resuscitated rats were then randomized into the normothermia (37°C) group, milder (35°C) group, mild (33°C) group, or moderate (28°C) group. Hypothermia was immediately induced with surface cooling. The target temperature was maintained for 4 h before rewarming to 37 ± 0.5°C. Moreover, at the end of the 4 h, a rat in each group was randomly selected to be sacrificed for the cerebral cortex electron microscopy observation (n = 1). The other resuscitated animals were observed for up to 72 h after ROSC (n = 7). Left ventricular ejection fraction (LVEF) and left ventricular end diastolic volume (LVEDV) were measured. Survival time, survival rate, and neurological deficit score (NDS) were recorded for 72 h.

Results

During hypothermia, higher LVEF was observed in the hypothermia groups when compared with normothermia group (35°C vs. 37°C, p < 0.05, 33°C and 28°C vs. 37°C, p < 0.01). Among the hypothermia groups, LVEF was higher in the 28°C group than that of 35°C (p < 0.05). However, both the heart rate (HR) (p < 0.01) and LVEDV (28°C vs. 35°C, p < 0.01, 28°C vs. 37°C and 33°C, p < 0.05) were lowest in the 28°C group when compared with the other groups. There were no significant differences of LVEF and LVEDV between the group 35°C and 33°C (p > 0.05). After rewarming, the LVEF of 35°C group was higher than that of group 37°C, 33°C, and 28°C (35°C vs. 37°C and 28°C, p < 0.01, 35°C vs. 33°C, p < 0.05). Group 35°C and 33°C resulted in longer survival (p < 0.01), higher survival rate (p < 0.01), and lower NDS (35°C vs. 37°C and 28°C, p < 0.01, 33°C vs. 37°C and 28°C, p < 0.05) compared with the group 37°C and 28°C. The extent of damage to cerebral cortex cells in group of 35°C and 33°C was lighter than that in group of 37°C and 28°C. The 35°C group spent less time in the process of cooling and rewarming than the group 33°C and 28°C (p < 0.01).

Conclusions

An almost equal protective effect of milder hypothermia (35°C) and mild hypothermia (33°C) in cardiac arrest (CA) rats was achieved with more predominant effect than moderate hypothermia (28°C) and normothermia (37°C). More importantly, shorter time spent in cooling and rewarming was required in the 35°C group, indicating its potential clinical application. These findings support the possible use of milder hypothermia (35°C) as a therapeutic agent for postresuscitation.

Hypothermia Advocates Functional Mitochondria and Alleviates Oxidative Stress to Combat Acetaminophen-Induced Hepatotoxicity

For years, moderate hypothermia (32 °C) has been proposed as an unorthodox therapy for liver injuries, with proven hepatoprotective potential. Yet, limited mechanistic understanding has largely denied its acceptance over conventional pharmaceuticals for hepatoprotection. Today, facing a high prevalence of acetaminophen-induced liver injury (AILI) which accounts for the highest incidence of acute liver failure, hypothermia was evaluated as a potential therapy to combat AILI. For which, transforming growth factor-α transgenic mouse hepatocytes (TAMH) were subjected to concomitant 5 mM acetaminophen toxicity and moderate hypothermic conditioning for 24 h. Thereafter, its impact on mitophagy, mitochondrial biogenesis, glutathione homeostasis and c-Jun N-terminal kinase (JNK) signaling pathways were investigated. In the presence of AILI, hypothermia displayed simultaneous mitophagy and mitochondrial biogenesis to conserve functional mitochondria. Furthermore, antioxidant response was apparent with higher glutathione recycling and repressed JNK activation. These effects were, however, unremarkable with hypothermia alone without liver injury. This may suggest an adaptive response of hypothermia only to the injured sites, rendering it favorable as a potential targeted therapy. In fact, its cytoprotective effects were displayed in other DILI of similar pathology as acetaminophen i.e., valproate- and diclofenac-induced liver injury and this further corroborates the mechanistic findings of hypothermic actions on AILI.

Moderate hypothermia induces protection against hypoxia/reoxygenation injury by enhancing SUMOylation in cardiomyocytes

Moderate hypothermia plays a major role in myocardial cell death as a result of hypoxia/reoxygenation (H/R) injury. However, few studies have investigated the molecular mechanisms of hypothermic cardioprotection. Several responses to stress and other cell functions are regulated by post‑translational protein modifications controlled by small ubiquitin‑like modifier (SUMO). Previous studies have established that high SUMOylation of proteins potentiates the ability of cells to withstand hypoxic‑ischemic stress. The level to which moderate hypothermia affects SUMOylation is not fully understood, as the functions of SUMOylation in the heart have not been studied in depth. The aim of the present study was to investigate the effect of moderate hypothermia (33˚C) on the protective functions of SUMOylation on myocardial cells. HL‑1 and H9c2 cells were treated with the hypoxia‑mimetic chemical CoCl2 and complete medium to simulate H/R injury. Hypothermia intervention was then administered. A Cell Counting kit‑8 assay was used to analyze cell viability. Mitochondrial membrane potential and the generation of reactive oxygen species (ROS) were used as functional indexes of mitochondria dysfunction. Bcl‑2 and caspase‑3 expression levels were analyzed by western blotting. The present results suggested that moderate hypothermia significantly increased SUMO1 and Bcl‑2 expression levels, as well as the mitochondrial membrane potential, but significantly decreased the expression levels of caspase‑3 and mitochondrial ROS. Thus, moderate hypothermia may enhance SUMOylation and attenuate myocardial H/R injury. Moreover, a combination of SUMOylation and moderate hypothermia may be a potential cardiovascular intervention.

Recent antiepileptic and neuroprotective applications of brain cooling

Hypothermia is a widely used clinical practice for neuroprotection and is a well-established method to mitigate the adverse effects of some clinical conditions such as reperfusion injury after cardiac arrest and hypoxic ischemic encephalopathy in newborns. The discovery, that lowering the core temperature has a therapeutic potential dates back to the early 20th century, but the underlying mechanisms are actively researched, even today. Especially, in the area of neural disorders such as epilepsy and traumatic brain injury, cooling has promising prospects. It is well documented in animal models, that the application of focal brain cooling can effectively terminate epileptic discharges. There is, however, limited data regarding human clinical trials. In this review article, we will discuss the main aspects of therapeutic hypothermia focusing on its use in treating epilepsy. The various experimental approaches and device concepts for focal brain cooling are presented and their potential for controlling and suppressing seizure activity are compared.

The Effect of Therapeutic Mild Hypothermia on Brain Microvascular Endothelial Cells During Ischemia-Reperfusion Injury

BACKGROUND

To determine the cerebral protective effects of mild hypothermia (MH) on cerebral microcirculation.

METHODS

We established ischemia-reperfusion (I/R) injury and MH treatment models with rat brain microvascular endothelial cells (RBMECs) in vitro and examined the apoptotic changes. The cultured RBMECs were randomly divided into the control group, I/R group, and MH group, which was further divided into two subgroups: intra-ischemia hypothermia (IIH) and post-ischemia hypothermia (PIH). Cell morphological changes were assessed using fluorescence microscopy. Apoptotic rates were obtained by flow cytometry. Expressions of caspase-3, Bax, and Bcl-2 were analyzed by Western blot.

RESULTS

I/R injury in vitro induced apoptosis of RBMECs. The apoptotic rates in the control group, I/R group, and MH group were 0.13, 19.04, and 13.13%, respectively (P < 0.01). Compared with the I/R group, the MH group showed a significant decrease in the number of apoptotic cells, mainly in stage I apoptotic cells (P < 0.0083). The caspase-3 and Bax expressions were significantly enhanced (P < 0.05) in RBMECs after I/R injury, while substantial decreases in Bcl-2 expression were noted (P < 0.05). Following MH intervention, the increase in caspase-3 and Bax expression was suppressed (P < 0.05), while Bcl-2 expression significantly increased. The apoptotic rates or protein expressions between the two subgroups were not different significantly (P > 0.05).

CONCLUSIONS

These results indicate that MH could inhibit RBMEC apoptosis by preventing pro-apoptotic cells and early apoptotic cells from progressing to intermediate and advanced stages. This may be due to the effect of MH on I/R-induced apoptotic gene expression changes.

Temperature Variability in a Modern Targeted Temperature Management Trial

OBJECTIVES

The Eurotherm3235 trial showed that therapeutic hypothermia was deleterious in patients with raised intracranial pressure following traumatic brain injury. We sought to ascertain if increased temperature variability within the first 48 hours, or for 7 days post randomization, were modifiable risk factors associated with poorer outcome.

DESIGN

Eurotherm3235 was a multicenter randomized controlled trial. Patients were randomized to receive either therapeutic hypothermia in addition to standard care or the later only. Mean moving range (mr) was used to stratify subjects into tertiles by the variability present in their core temperature within the first 48 hours post randomization and within 7 days post randomization. The primary outcome measure was a collapsed Glasgow Outcome Scale-Extended at 6 months post randomization. The temperature variability effect was estimated with ordinal logistic regression adjusted for baseline covariates and treatment effect.

SETTING

Forty-seven critical care units in 18 countries.

PATIENTS

Patients enrolled in the Eurotherm3235 trial to either therapeutic hypothermia or control treatments only.

MEASUREMENTS AND MAIN RESULTS

Three hundred eighty-six patients were included in our study. High level of temperature variability during the first 48 hours was associated with poorer collapsed Glasgow Outcome Scale-Extended. This effect remained statistically significant when only the control arm of the study was analyzed. No statistically significant effect was seen within the first 48 hours in the hypothermia group or within 7 days in either group.

CONCLUSIONS

When targeting normothermia, temperature variability may be a statistically significant variable in an ordinal analysis adjusted for baseline covariates.

Loss of thioredoxin 2 alters mitochondrial respiratory function and induces cardiomyocyte hypertrophy

Thioredoxin 2 (Trx2), as a member of the thioredoxin system in mitochondria, is involved in controlling mitochondrial redox state. However, the role of Trx2 in cardiac biology is not fully understood. In the present study, the expression of Trx2 is silenced in quiescent neonatal rat ventricular cardiomyocytes (NRVCs) and mitochondrial respiratory function and cardiomyocyte hypertrophy are assessed. The results show that Trx2 depletion does not induce significant cytotoxicity in quiescent NRVCs. Remarkably, Trx2 depletion results in cardiomyocyte hypertrophy as determined by increased cell size and protein synthesis. Furthermore, Trx2 depletion inhibits AMPK activity and AMPK activator reversed cellular hypertrophy. Trx2 depletion enhances mitochondrial ROS generation without impact on cellular ROS level. Trx2 depletion has no effect on mitochondrial biogenesis. Specifically, Trx2 depletion increases mitochondrial respiration flux and total ATP concentration under quiescent conditions. To decipher the relationship between ROS generation, mitochondrial respiration flux, and AMPK signaling, mitochondrial metabolism and ROS was specifically inhibited, and the results show that AMPK inactivation and hypertrophic response in Trx2-silenced cells is reversed by respiration blockers but not ROS scavenger. In conclusion, these results show that beyond mitochondrial ROS scavenging, Trx2 controls mitochondrial respiratory function in quiescent cardiomyocytes and is implicated in cardiomyocyte hypertrophy via AMPK signaling.

Bone mesenchymal stem cells transplantation combined with mild hypothermia improves the prognosis of cerebral ischemia in rats

Bone marrow mesenchymal stem cells (BMSCs) are used as a great promising choice for the treatment of cerebral ischemia. Herein, we discuss the neuroprotective effects of the combination of BMSCs transplantation and mild hypothermia (MH) in an ischemia-reperfusion rat model. First, BMSCs were isolated using density gradient centrifugation and the adherent screening method, followed by culture, identification and labeling with DAPI. Second, adult male SD rats were divided into 5 groups: sham group (surgery without blockage of middle cerebral artery), model group (middle cerebral artery occlusion (MCAO) was established 2h prior to reperfusion), BMSCs group (injection of BMSCs via the lateral ventricle 24h after MCAO), MH group (mild hypothermia for 3h immediately after MCAO) and combination therapy group (combination of BMSCs and MH). Finally, the modified neurological severity score (mNSS) test was performed to assess behavioral function at different time points (before MCAO, before transplantation, at day 1, day 5 and day 10 after transplantation). After that, the brain was subjected to TTC staining, and the homing and angiogenesis were evaluated by immumofluorescence and immunohistochemistry. Immunofluorescence staining and Western Blot analysis were performed to calculate the percentage of the infarct area and explore glial fibrillary acidic protein (GFAP) and vascular endothelial growth factor (VEGF). Our results showed that the combination therapy significantly decreased mNSS scores (P<0.01) and reduced the percentage of the infarct area (P<0.01) than a single treatment. Moreover, the expression of GFAP and VEGF increased significantly in the combination therapy group (at day 5, day 10 after transplantation; at all time points after transplantation, respectively) compared to the single treatment groups. Taken together, it was suggested that the combination of BMSCs transplantation and MH can significantly reduce the percentage of the infarct area and improve functional recovery by promoting homing and angiogenesis, which may be a beneficial treatment for cerebral ischemia.

Mild Hypothermia Pretreatment Attenuates Liver Ischemia Reperfusion Injury Through Inhibiting c-Jun NH2-terminal Kinase Phosphorylation in Rats

BACKGROUND

Mild hypothermia is known to be protected against ischemia reperfusion (IR) injury. But the exact mechanisms of protection have not yet been fully understood and its usage has been limited. Mild hypothermia pretreatment (MHP) is used to investigate the mechanisms of the protective effects against liver IR injury.

METHODS

Anesthetized male Sprague-Dawley rats were randomly divided into five groups including the normal group (N), sham group (S), MHP group, normothermia pretreatment (NP) + IR group, and the MHP + IR group. In the pretreatment groups, mild hypothermia (32.2 ± 0.3°C) and normothermia (37 ± 0.5°C) pretreatment were applied for 2 hours, respectively. Then the IR groups suffered partial (70%) hepatic ischemia for 1 hour and reperfusion for 6 hours. At last, hepatic injury, apoptosis, and protein expression were assessed.

RESULTS

Levels of serum alanine transaminase, hepatic injury, hepatocyte apoptosis, and c-Jun N-terminal kinase (JNK) phosphorylation were significantly higher in the IR groups. But when compared to NP, all these changes induced by IR were markedly attenuated by MHP. Serum alanine transaminase levels were 383.4 ± 13.1U/L in the MHP + IR group and 951.3 ± 39.4 U/L in the NP + IR group. The histologic score of liver injury in the MHP + IR group was 4.83 ± 1.17, whereas in the NP + IR group it was 10.5 ± 1.05. The proportion of apoptotic cells in the MHP + IR group was 11.58 ± 0.60, but in the NP + IR group, it was 44.95 ± 1.61. The phosphorylation of JNK was also significantly reduced in the MHP + IR group. All these differences are statistically significant (P < .05).

CONCLUSIONS

MHP could markedly reduce liver IR injury, and these protective effects may be mainly exerted via inhibition of JNK phosphorylation.

CTHRC1 mediates IL‑1β‑induced apoptosis in chondrocytes via JNK1/2 signaling

Osteoarthritis (OA), also known as degenerative joint disease or degenerative arthritis, is characterized by chondrocyte apoptosis. The aim of the present study was to investigate the effects of collagen triple helix repeat containing 1 (CTHRC1) and the c‑Jun N‑terminal kinase (JNK) 1/2 inhibitor SP600125 on rat chondrocytes cultured in vitro with interleukin (IL)‑1β. Chondrocytes were treated with different doses of IL‑1β and cell viability and CTHRC1 expression were assessed using Cell Counting Kit‑8 and western blot assays, respectively. In separate experiments, chondrocytes were treated with CTHRC1‑expressing constructs (pLVX‑Puro‑CTHRC1) and/or SP600125, or IL‑1β with either CTHRC1 short hairpin (sh)RNA constructs (shNRA‑CTHRC1) or SP600125. The expression of CTHRC1, B‑cell lymphoma (Bcl)‑2, Bcl‑2‑associated X protein (Bax), cleaved caspase‑3, poly ADP ribose polymerase (PARP)‑1 and matrix metalloproteinase (MMP)‑13 was measured using reverse transcription‑quantitative polymerase chain reaction and western blotting assays. A Cell Counting Kit‑8 assay was performed to examine cell viability. Annexin V/propidium iodide staining and flow cytometry assays were used to detect chondrocyte apoptosis. The expression of JNK1/2 and phosphorylated JNK1/2 was measured using western blotting. CTHRC1 was highly expressed in patients with OA compared with normal controls. IL‑1β treatment (5, 10 and 20 ng/ml) increased the protein expression of CTHRC1 in a dose‑dependent manner and decreased the viability of chondrocytes in a time‑dependent manner. pLVX‑Puro‑CTHRC1 mimics the effect of IL‑1β on chondrocyte apoptosis and JNK1/2 activity, and this is reversed by SP600125 treatment. However, transfection with shRNA‑CTHRC1 or treatment with SP600125 inhibited IL‑1β‑induced cell apoptosis and JNK1/2 activation. These results indicate that CTHRC1 downregulation may protect chondrocytes from IL‑1β‑induced apoptosis by inactivating the JNK1/2 pathway.

Mild hypothermia protects neurons against oxygen glucose deprivation via poly (ADP-ribose) signaling

OBJECTIVE

Hypothermia is a neuroprotective mechanism that has been validated for use in alleviating neonatal hypoxic-ischemic (HI) brain injury. Nevertheless, it is unclear whether poly (ADP-ribose) (PAR) signaling is involved in hypothermia-induced neuroprotection. In this study, we investigated whether mild hypothermia rescues oxygen glucose deprivation (OGD)-induced cell death by modifying PAR-relative protein expression, such as AIF, PARP-1, and PAR polymer, in primary-cultured hippocampal neurons.

METHODS

We analyzed neuronal morphology and related protein expression of PAR signaling after OGD followed by mild hypothermia in primary-cultured newborn hippocampal neurons.

RESULTS

Hypothermic treatment resulted in improved neuronal viability and alleviated DNA damage. Results from the protein assay showed that hypothermia attenuated nuclear translocation of apoptosis-inducing factor (AIF), inhibited overactivation of poly(ADP-ribose) polymerase-1 (PARP-1), and decreased production of PAR polymer induced by PARP-1 activation after OGD.

CONCLUSIONS

These results showed that mild hypothermia partially protects immature hippocampal neurons against OGD injury in part by interfering with the PAR signaling pathway.

Effect of hypothermia on apoptosis in traumatic brain injury and hemorrhagic shock model

INTRODUCTION

The neuroprotective mechanisms of therapeutic hypothermia against trauma-related injury have not been fully understood yet. In this study, we aimed to investigate the effects of therapeutic hypothermia on biochemical and histopathological markers of apoptosis using Traumatic brain injury (TBI) and hemorrhagic shock (HS) model.

METHODS

A total of 50 male albino-wistar rats were divided into five groups: Group isolated TBI, Group NT (HT+HS+normothermia), Group MH (HT+HS+mild hypothermia), Group MoH (HT+HS+moderate hypothermia) and Group C (control). Neurological deficit scores were assessed at baseline and at 24h. The rats were, then, sacrificed to collect serum and brain tissue samples. Levels of Caspase-3,6,8, proteoglycan-4 (PG-4), malondialdehyde (MDA), and nitric oxide (NO) were measured in serum and brain tissue samples. Histopathological examination was performed in brain tissue.

RESULTS

There were significant differences in the serum levels of Caspase-3 between Group NT and Group C (p=0.018). The serum levels of Caspase-6 in Group NT (0.70±0.58) were lower than Group MH (1.39±0.28), although the difference was not statistically significant (p=0.068). There were significant differences in the brain tissue samples for Caspase-3 levels between Group NT and Group C (p=0.049). A significant difference in the Caspase-8 brain tissue levels was also observed between Group NT and Group C (p=0.022). Group NT had significantly higher scores of all the pathological variables (for edema p<0.017; for gliosis p<0.001; for congestion p<0.003, for hemorrhage p<0.011) than Group C.

CONCLUSION

Our study results suggest that hypothermia may exert its neuroprotective effects by reducing markers of apoptotic pathway, particularly Caspase-3 on TBI and HS.

PD149163 induces hypothermia to protect against brain injury in acute cerebral ischemic rats

Therapeutic hypothermia is a promising strategy for acute cerebral ischemia via physical or pharmacological methods. In this study, we pharmacologically induced hypothermia on Sprague Dawley rats by intraperitoneally injecting PD149163. We found that mild hypothermia was induced by PD149163 treatment without local cerebral blood flow (LCBF) alteration. To evaluate the neuroprotective effects of PD149163, TTC staining, HE staining and Nissl's staining were performed in our study. We found that PD149163 could prevent neuronal damage, and inhibit proliferation and activation of glial cells induced by ischemia. Simultaneously, we observed PD149163 ameliorated apoptosis characterized by down-regulated caspase-3 and Bax, but elevated Bcl-2. Moreover, PD149163 dramatically reduced JNK and AMPK/mTOR signaling pathway activation, and thereby inhibited autophagy by increased P62 expression, decreased the ratio of LC₃-Ⅱ to LC₃-Ⅰ and the expression of Beclin. Taken together, the present findings reveal the therapeutic effects of PD149163-induced hypothermia in brain ischemia, and provide a new strategy for stroke treatment.

The Role of Peroxisome Proliferator-Activated Receptor γ in Mediating Cardioprotection Against Ischemia/Reperfusion Injury

Myocardial infarction (MI) is a serious cardiovascular disease resulting in high rates of morbidity and mortality. Although advances have been made in restoring myocardial perfusion in ischemic areas, decreases in cardiomyocyte death and infarct size are still limited, attributing to myocardial ischemia/reperfusion (I/R) injury. It is necessary to develop therapies to restrict myocardial I/R injury and protect cardiomyocytes against further damage after MI. Many studies have suggested that peroxisome proliferator-activated receptor γ (PPARγ), a ligand-inducible nuclear receptor that predominantly regulates glucose and lipid metabolism, is a promising therapeutic target for ameliorating myocardial I/R injury. Thus, this review focuses on the role of PPARγ in cardioprotection during myocardial I/R. The cardioprotective effects of PPARγ, including attenuating oxidative stress, inhibiting inflammatory responses, improving glucose and lipid metabolism, and antagonizing apoptosis, are described. Additionally, the underlying mechanisms of cardioprotective effects of PPARγ, such as regulating the expression of target genes, influencing other transcription factors, and modulating kinase signaling pathways, are further discussed.

Moderate therapeutic hypothermia induces multimodal protective effects in oxygen-glucose deprivation/reperfusion injured cardiomyocytes

OBJECTIVE

Therapeutic hypothermia has been shown to attenuate myocardial cell death due to ischemia/reperfusion injury. However, cellular mechanisms of cooling remain to be elucidated. Especially during reperfusion, mitochondrial dysfunction contributes to cell death by releasing apoptosis inductors. The aim of the present study was to investigate the effects of moderate therapeutic hypothermia (33.5°C) on mitochondrial mediated apoptosis in ischemia/reperfusion-injured cardiomyocytes.

METHODS

Ischemic injury was simulated by oxygen-glucose deprivation for 6h in glucose/serum-free medium at 0.2% O₂ in mouse atrial HL-1 cardiomyocytes. Simulation of reperfusion was achieved by restoration of nutrients in complete supplemented medium and incubation at 21% O₂. Early application of therapeutic hypothermia, cooling during the oxygen-glucose deprivation phase, was initiated after 3h of oxygen-glucose deprivation and maintained for 24h. Mitochondrial membrane integrity was assessed by cytochrome c and AIF protein releases. Furthermore, mitochondria were stained with MitoTracker Red and intra-cellular cytochrome c localization was visualized by immunofluorescence staining. Moreover, anti-apoptotic Bcl-2 and Hsp70 as well as phagophore promoting LC3-II protein expressions were analyzed by Western-blot analysis.

RESULTS

Therapeutic hypothermia initiated during oxygen-glucose deprivation significantly reduced mitochondrial release of cytochrome c and AIF in cardiomyocytes during reperfusion. Secondly, anti-apoptotic Bcl-2/Bax ratio and Hsp70 protein expressions were significantly upregulated due to hypothermia, indicating an inhibition of both caspase-dependent and -independent apoptosis. Furthermore, cardiomyocytes treated with therapeutic hypothermia showed increased LC3-II protein levels associated with the mitochondria during the first 3h of reperfusion, indicating the initiation of phagophores formation and sequestration of presumably damaged mitochondrion.

CONCLUSION

Early application of therapeutic hypothermia effectively inhibited cardiomyocyte cell death due to oxygen-glucose deprivation/reperfusion-induced injury via multiple pathways. As hypothermia preserved mitochondrial membrane integrity, which resulted in reduced cytochrome c and AIF releases, induction of both caspase-dependent and -independent apoptosis was minimized. Secondly, cooling attenuated intrinsic apoptosis via Hsp70 upregulation and increasing anti-apoptotic Bcl-2/Bax ratio. Moreover, therapeutic hypothermia promoted mitochondrial associated LC3-II during the early phase of reperfusion, possibly leading to the sequestration and degradation of damaged mitochondrion to attenuate the activation of cell death.

Angiotensin II promotes the anticoagulant effects of rivaroxaban via angiotensin type 2 receptor signaling in mice

Rivaroxaban is an oral direct factor Xa inhibitor approved for the treatment of stroke and systemic thromboembolism in patients with non-valvular atrial fibrillation. Despite its efficacy, rivaroxaban therapy results in adverse effects and complications, such as bleeding. Angiotensin II (AngII) is implicated in many cardiovascular conditions, such as hypertension and heart failure. In this study, we investigate whether AngII influences anticoagulant effects of rivaroxaban by using an experimental mouse model with type 2 diabetes mellitus and advanced glycation end product (AGE)-exposed human umbilical vein endothelial cells (HUVECs). We found that AngII promoted the anticoagulant effects of rivaroxaban in KKAy mice. The combination of rivaroxaban and AngII enhanced in vivo tissue factor pathway inhibitor (TFPI) activity and induced TFPI expression and activity in AGE-exposed HUVECs. Angiotensin type 2 receptor (AT2R) and Mas antagonists attenuated the AngII-enhanced anticoagulant action of rivaroxaban in vivo, and abolished the increased endothelial TFPI expression and activity. However, angiotensin type 1 receptor (AT1R) antagonist exerted no effects. Additionally, combination of rivaroxaban and AngII induced aortic AT2R and Mas expression. Our data suggest that the anticoagulant effects of rivaroxaban are promoted by AngII via AT2R and Mas signaling. These findings are significant for the clinical administration of rivaroxaban.

Donation After Circulatory Death Lungs Transplantable Up to Six Hours After Ex Vivo Lung Perfusion

BACKGROUND

Despite the critical need for donor lungs, logistic and geographic barriers hinder lung utilization. We hypothesized that lungs donated after circulatory death subjected to 6 hours of cold preservation after ex vivo lung perfusion (EVLP) would have similar outcomes after transplantation as lungs transplanted immediately after EVLP, and that both would perform superiorly compared with lungs transplanted immediately after procurement.

METHODS

Donor porcine lungs were procured after circulatory death and 15 minutes of warm ischemia. Three groups (n = 5 per group) were randomized: immediate left lung transplantation (Immediate group), EVLP for 4 hours followed by transplantation (EVLP group), or EVLP for 4 hours followed by 6 hours of cold preservation followed by transplantation (EVLP+Cold group). Lungs were reperfused for 2 hours before obtaining pulmonary vein samples for partial pressure of oxygen/fraction of inspired oxygen ratio calculations, airway pressures for compliance measurements, and wet/dry weight ratios.

RESULTS

The partial pressure of oxygen/fraction of inspired oxygen ratios in the EVLP and EVLP+Cold groups were significantly improved compared with those in the Immediate group (429.7 ± 51.8 and 436.7 ± 48.2 versus 117.4 ± 22.9 mm Hg, respectively). In addition, dynamic compliance was significantly improved in the EVLP and EVLP+Cold groups compared with immediate group (26.2 ± 4.2 and 27.9 ± 3.5 versus 11.1 ± 2.4 mL/cmH₂O, respectively). There were no differences in oxygenation capacity or dynamic compliance between the EVLP and EVLP+Cold groups. Inflammatory cytokine levels were significantly lower in the EVLP and EVLP+Cold groups.

CONCLUSIONS

Lungs donated after circulatory death can be successfully transplanted as much as 6 hours after EVLP. Cold preservation of lungs after ex vivo assessment and rehabilitation may improve organ allocation, even to distant recipients, without compromising allograft function.

Protection against doxorubicin-induced myocardial dysfunction in mice by cardiac-specific expression of carboxyl terminus of hsp70-interacting protein

Carboxyl terminus of Hsp70-interacting protein (CHIP) is a critical ubiquitin ligase/cochaperone to reduce cardiac oxidative stress, inflammation, cardiomyocyte apoptosis and autophage etc. However, it is unclear whether overexpression of CHIP in the heart would exert protective effects against DOX-induced cardiomyopathy. Cardiac-specific CHIP transgenic (CHIP-TG) mice and the wild-type (WT) littermates were treated with DOX or saline. DOX-induced cardiac atrophy, dysfunction, inflammation, oxidative stress and cardiomyocyte apoptosis were significantly attenuated in CHIP-TG mice. CHIP-TG mice also showed higher survival rate than that of WT mice (40% versus 10%) after 10-day administration of DOX. In contrast, knockdown of CHIP by siRNA in vitro further enhanced DOX-induced cardiotoxic effects. Global gene microarray assay revealed that after DOX-treatment, differentially expressed genes between WT and CHIP-TG mice were mainly involved in apoptosis, atrophy, immune/inflammation and oxidative stress. Mechanistically, CHIP directly promotes ubiquitin-mediated degradation of p53 and SHP-1, which results in activation of ERK1/2 and STAT3 pathways thereby ameliorating DOX-induced cardiac toxicity.

Subdural hematoma decompression model: A model of traumatic brain injury with ischemic-reperfusional pathophysiology: A review of the literature

The prognosis for patients with traumatic brain injury (TBI) with subdural hematoma (SDH) remains poor. In accordance with an increasing elderly population, the incidence of geriatric TBI with SDH is rising. An important contributor to the neurological injury associated with SDH is the ischemic damage which is caused by raised intracranial pressure (ICP) producing impaired cerebral perfusion. To control intracranial hypertension, the current management consists of hematoma evacuation with or without decompressive craniotomy. This removal of the SDH results in the immediate reversal of global ischemia accompanied by an abrupt reduction of mass lesion and an ensuing reperfusion injury. Experimental models can play a critical role in improving our understanding of the underlying pathophysiology and in exploring potential treatments for patients with SDH. In this review, we describe the epidemiology, pathophysiology and clinical background of SDH.

Targeted temperature management in traumatic brain injury

Traumatic brain injury (TBI) is recognized as the significant cause of mortality and morbidity in the world. To reduce unfavorable outcome in TBI patients, many researches have made much efforts for the innovation of TBI treatment. With the results from several basic and clinical studies, targeted temperature management (TTM) including therapeutic hypothermia (TH) have been recognized as the candidate of neuroprotective treatment. However, their evidences are not yet proven in larger randomized controlled trials (RCTs). The main aim of this review is thus to clarify specific pathophysiology which TTM will be effective in TBI. Historically, there were several clinical trials which compare TH and normothermia. Recently, two RCTs were able to demonstrate the significant beneficial effects of TTM in one specific pathology, patients with mass evacuated lesions. These suggested that TTM might be effective especially for the ischemic-reperfusional pathophysiology of TBI, like as acute subdural hematoma which needs to be evacuated. Also, the latest preliminary report of European multicenter trial suggested the promising efficacy of reduction of intracranial pressure in TBI. Conclusively, TTM is still in the center of neuroprotective treatments in TBI. This therapy is expected to mitigate ischemic and reperfusional pathophysiology and to reduce intracranial pressure in TBI. Further results from ongoing clinical RCTs are waited.

Therapeutic hypothermia in the intensive cardiac care unit

Therapeutic hypothermia has demonstrated to improve both survival and neurological outcome in patients who experienced an out-of-hospital cardiac arrest. Nevertheless, many aspects of its clinical application are still controversial. Current guidelines recommend to cool patients who survive a cardiac arrest due to either ventricular fibrillation or ventricular tachycardia, whereas the beneficial effect of lowering body temperature in nonshockable rhythms is still questionable due to the lack of randomized controlled trial involving this subgroup of patients. Although therapeutic hypothermia is often begun before hospital arrival, the optimal time to start cooling is still a matter of debate. Furthermore, different methods are available to low body temperature, but no direct comparisons are available to establish which device performs better than others, and a combination of external and endovascular cooling is usually preferred. The present review is aimed at summarizing the available evidence supporting the use in clinical practice of mild hypothermia in comatose survivors from cardiac arrest and at evaluating its adverse events and their treatment.

Therapeutic effect of tPA in ischemic stroke is enhanced by its combination with normobaric oxygen and hypothermia or ethanol

BACKGROUND AND PURPOSE

Our lab has previously elucidated the neuroprotective effects of normobaric oxygen (NBO) and ethanol (EtOH) in ischemic stroke. The present study further evaluated the effect of EtOH or hypothermia (Hypo) in the presence of low concentration of NBO and determined whether EtOH can substitute hypothermia in a more clinically relevant autologous embolus rat stroke model in which reperfusion was established by tissue-type plasminogen activator (t-PA).

METHODS

At 1h of middle cerebral artery occlusion (MCAO) by an autologous embolus, rats received t-PA. In addition, at the same time, ischemic animals were treated with either EtOH (1.0 g/kg) or hypothermia (33°C for 3h) in combination with NBO (60% for 3h). Extent of neuroprotection was assessed by apoptotic cell death measured by ELISA and Western immunoblotting analysis for pro- (AIF, activated Caspase-3, Bax) and anti-apoptotic (Bcl-2) protein expression at 3 and 24h of reperfusion induced by t-PA administration.

RESULTS

Compared to ischemic rats treated only with t-PA, animals with NBO, hypothermia or EtOH had significantly reduced apoptotic cell death by 32.5%, 43.1% and 36.0% respectively. Furthermore, combination therapy that included NBO+EtOH or NBO+Hypo with t-PA exhibited a much larger decline (p<0.01) in the cell death by 71.1% and 73.6%, respectively. Similarly, NBO+EtOH or NBO+Hypo treatment in addition to t-PA enhanced beneficial effects on both pro- and anti-apoptotic protein expressions as compared to other options.

CONCLUSIONS

Neuroprotection after stroke can be enhanced by combination treatment with either EtOH or hypothermia in the presence of t-PA and 60% NBO. Because the effects produced by EtOH and hypothermia are comparable, their mechanism of action may be not only similar but also could be interchangeable in future clinical trials.

Moderate hypothermia ameliorates enterocyte mitochondrial dysfunction in severe shock and reperfusion

BACKGROUND

Hypothermia can ameliorate ischemia-reperfusion-induced intestinal injury; however, whether the therapeutic mechanism of hypothermia on hemorrhagic shock, a severe condition of ischemia-reperfusion, is associated with mitochondrial protection in enterocytes is rarely reported. We aimed to evaluate the effects of hypothermia on mitochondria after shock-induced intestinal injury.

MATERIALS AND METHODS

A severe hemorrhagic shock model was constructed in Sprague-Dawley rats at induced hypothermic (32°C or 34°C) or normothermic temperatures (37°C), followed by resuscitation with whole shed blood and Ringer lactate (15 mg/kg body weight). After 2 h, 24 rats were killed and their intestinal tissue was collected; the remaining animals were returned to the normothermic environment to observe the survival time.

RESULTS

There was severe mitochondrial dysfunction in the normothermia group, as well as increased oxidative stress and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling apoptotic index. As expected, hypothermia treatment decreased mitochondrial permeability transition pore opening and restored the mitochondrial membrane potential and intracellular adenosine triphosphate content. Furthermore, hypothermia elevated mitochondrial-reduced glutathione and decreased mitochondrial malondialdehyde; consistent with the restored mitochondrial function, intestinal cell apoptosis and intestinal histopathologic injury were attenuated, the systemic inflammatory response was mitigated, and survival time was significantly prolonged. Additionally, moderate-induced hypothermia (32°C) had better therapeutic effects than mild hypothermia (34°C).

CONCLUSIONS

The results suggest that moderate hypothermia resuscitation is an effective treatment for shock-induced intestinal injury, and its therapeutic mechanism may be related to mitochondrial protection.

The pathways by which mild hypothermia inhibits neuronal apoptosis following ischemia/reperfusion injury

Several studies have demonstrated that mild hypothermia exhibits a neuroprotective role and it can inhibit endothelial cell apoptosis following ischemia/reperfusion injury by decreasing caspase-3 expression. It is hypothesized that mild hypothermia exhibits neuroprotective effects on neurons exposed to ischemia/reperfusion condition produced by oxygen-glucose deprivation. Mild hypothermia significantly reduced the number of apoptotic neurons, decreased the expression of pro-apoptotic protein Bax and increased mitochondrial membrane potential, with the peak of anti-apoptotic effect appearing between 6 and 12 hours after the injury. These findings indicate that mild hypothermia inhibits neuronal apoptosis following ischemia/reperfusion injury by protecting the mitochondria and that the effective time window is 6-12 hours after ischemia/reperfusion injury.

Mild hypothermia as a treatment for central nervous system injuries: Positive or negative effects

Besides local neuronal damage caused by the primary insult, central nervous system injuries may secondarily cause a progressive cascade of related events including brain edema, ischemia, oxida-tive stress, excitotoxicity, and dysregulation of calcium homeostasis. Hypothermia is a beneficial strategy in a variety of acute central nervous system injuries. Mild hypothermia can treat high intra-cranial pressure following traumatic brain injuries in adults. It is a new treatment that increases sur-vival and quality of life for patients suffering from ischemic insults such as cardiac arrest, stroke, and neurogenic fever following brain trauma. Therapeutic hypothermia decreases free radical produc-tion, inflammation, excitotoxicity and intracranial pressure, and improves cerebral metabolism after traumatic brain injury and cerebral ischemia, thus protecting against central nervous system dam-age. Although a series of pathological and physiological changes as well as potential side effects are observed during hypothermia treatment, it remains a potential therapeutic strategy for central nervous system injuries and deserves further study.

TXNIP mediates NLRP3 inflammasome activation in cardiac microvascular endothelial cells as a novel mechanism in myocardial ischemia/reperfusion injury

NLRP3 inflammasome is necessary for initiating acute sterile inflammation. Recent studies have demonstrated that NLRP3 inflammasome is up-regulated and mediates myocardial ischemia/reperfusion (MI/R) injury. However, the signaling pathways that lead to the activation of NLRP3 inflammasome by MI/R injury have not been fully elucidated. C57BL/6J mice were subjected to 30 min ischemia and 3 or 24 h reperfusion. The ischemic heart exhibited enhanced inflammasome activation as evidenced by increased NLRP3 expression and caspase-1 activity and increased IL-1β and IL-18 production. Intramyocardial NLRP3 siRNA injection or an intraperitoneal injection of BAY 11-7028, an inflammasome inhibitor, attenuated macrophage and neutrophil infiltration and decreased MI/R injury, as measured by cardiomyocyte apoptosis and infarct size. The ischemic heart also exhibited enhanced interaction between Txnip and NLRP3, which has been shown to be a mechanism for activating NLRP3. Intramyocardial Txnip siRNA injection also decreased infarct size and NLRP3 activation. In vitro experiments revealed that NLRP3 was expressed in cardiac microvascular endothelial cells (CMECs), but was hardly expressed in cardiomyocytes. Simulated ischemia/reperfusion (SI/R) stimulated NLRP3 inflammasome activation in CMECs, but not in cardiomyocytes. Moreover, CMECs subjected to SI/R injury increased interactions between Txnip and NLRP3. Txnip siRNA diminished NLRP3 inflammasome activation and SI/R-induced injury, as measured by LDH release and caspase-3 activity in CMECs. ROS scavenger dissociated TXNIP from NLRP3 and inhibited the activation of NLRP3 inflammasome in the CMECs. For the first time, we demonstrated that TXNIP-mediated NLRP3 inflammasome activation in CMECs was a novel mechanism of MI/R injury. Interventions that block Txnip/NLRP3 signaling to inhibit the activation of NLRP3 inflammasomes may be novel therapies for mitigating MI/R injury.

Oxidative stress and antioxidant activity in hypothermia and rewarming: can RONS modulate the beneficial effects of therapeutic hypothermia?

Hypothermia is a condition in which core temperature drops below the level necessary to maintain bodily functions. The decrease in temperature may disrupt some physiological systems of the body, including alterations in microcirculation and reduction of oxygen supply to tissues. The lack of oxygen can induce the generation of reactive oxygen and nitrogen free radicals (RONS), followed by oxidative stress, and finally, apoptosis and/or necrosis. Furthermore, since the hypothermia is inevitably followed by a rewarming process, we should also consider its effects. Despite hypothermia and rewarming inducing injury, many benefits of hypothermia have been demonstrated when used to preserve brain, cardiac, hepatic, and intestinal function against ischemic injury. This review gives an overview of the effects of hypothermia and rewarming on the oxidant/antioxidant balance and provides hypothesis for the role of reactive oxygen species in therapeutic hypothermia.

Preoperative-induced mild hypothermia attenuates neuronal damage in a rat subdural hematoma model

Post-traumatic hypothermia has been effective for traumatic brain injury in the laboratory setting. However, hypothermia has not shown efficacy in clinical trials. With the results of a recent clinical trial, we hypothesized that hypothermia might reduce neuronal damage in acute subdural hematoma (ASDH) by blunting the effects of reperfusion injury. Twenty rats were induced with ASDH and placed into one of four groups. The normothermia group was maintained at 37 °C throughout. In the early hypothermia group, brain temperature was reduced to 33 °C 30 min prior to craniotomy. In the late hypothermia group, brain temperature was lowered to 33 °C 30 min after decompression. The sham group had no ASDH and underwent only craniotomy with normothermia. For estimation of glial and neuronal cell damage, we analyzed serum and microdialysate (using a 100kD probe) concentrations of: glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl--terminal hydrolase -L1 (UCH-L1). Hypothermia induced early significantly reduced the concentration of MD UCH-L1. In conclusion, hypothermia induced early may reduce neuronal cell damage in the reperfusion injury, which was induced after ASDH removal. MD UCH-L1 seems like a good -candidate for a sensitive microdialysate biomarker for -neuronal injury and outcome.

Glucagon-like peptide-1 preserves coronary microvascular endothelial function after cardiac arrest and resuscitation: potential antioxidant effects

Glucagon-like peptide-1 (GLP-1) has protective effects in the heart. We hypothesized that GLP-1 would mitigate coronary microvascular and left ventricular (LV) dysfunction if administered after cardiac arrest and resuscitation (CAR). Eighteen swine were subjected to ventricular fibrillation followed by resuscitation. Swine surviving to return of spontaneous circulation (ROSC) were randomized to receive an intravenous infusion of either human rGLP-1 (10 pmol·kg(-1)·min(-1); n = 8) or 0.9% saline (n = 8) for 4 h, beginning 1 min after ROSC. CAR caused a decline in coronary flow reserve (CFR) in control animals (pre-arrest, 1.86 ± 0.20; 1 h post-ROSC, 1.3 ± 0.05; 4 h post-ROSC, 1.25 ± 0.06; P < 0.05). GLP-1 preserved CFR for up to 4 h after ROSC (pre-arrest, 1.31 ± 0.17; 1 h post-ROSC, 1.5 ± 0.01; 4 h post-ROSC, 1.55 ± 0.22). Although there was a trend toward improvement in LV relaxation in the GLP-1-treated animals, overall LV function was not consistently different between groups. 8-iso-PGF(2α), a measure of reactive oxygen species load, was decreased in post-ROSC GLP-1-treated animals [placebo, control (NS): 38.1 ± 1.54 pg/ml; GLP-1: 26.59 ± 1.56 pg/ml; P < 0.05]. Infusion of GLP-1 after CAR preserved coronary microvascular and LV diastolic function. These effects may be mediated through a reduction in oxidative stress.

Neuroprotective effect of preoperatively induced mild hypothermia as determined by biomarkers and histopathological estimation in a rat subdural hematoma decompression model

OBJECT

In patients who have sustained a traumatic brain injury (TBI), hypothermia therapy has not shown efficacy in multicenter clinical trials. Armed with the post hoc data from the latest clinical trial (National Acute Brain Injury Study: Hypothermia II), the authors hypothesized that hypothermia may be beneficial in an acute subdural hematoma (SDH) rat model by blunting the effects of ischemia/reperfusion injury. The major aim of this study was to test the efficacy of temperature management in reducing brain damage after acute SDH.

METHODS

The rats were induced with acute SDH and placed into 1 of 4 groups: 1) normothermia group (37°C); 2) early hypothermia group, head and body temperature reduced to 33°C 30 minutes prior to craniotomy; 3) late hypothermia group, temperature lowered to 33°C 30 minutes after decompression; and 4) sham group, no acute SDH (only craniotomy with normothermia). To assess for neuronal and glial cell damage, the authors analyzed microdialysate concentrations of GFAP and ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) by using a 100-kD probe. Fluoro-Jade B-positive neurons and injury volume with 2,3,5-triphenyltetrazolium chloride staining were also measured.

RESULTS

In the early phase of reperfusion (30 minutes, 2.5 hours after decompression), extracellular UCH-L1 in the early hypothermia group was significantly lower than in the normothermia group (early, 4.9 ± 1.0 ng/dl; late, 35.2 ± 12.1 ng/dl; normothermia, 50.20 ± 28.3 ng/dl; sham, 3.1 ± 1.3 ng/dl; early vs normothermia, p < 0.01; sham vs normothermia, p < 0.01, analyzed using ANOVA followed by a post hoc Bonferroni test). In the late phase of reperfusion (> 2.5 hours after decompression), extracellular GFAP in the early hypothermia group was also lower than in the normothermia and late hypothermia groups (early, 5.5 ± 2.9 ng/dl; late, 7.4 ± 3.4 ng/dl; normothermia, 15.3 ± 8.4 ng/dl; sham, 3.3 ± 1.0 ng/dl; normothermia vs sham; p < 0.01). The number of Fluoro-Jade B-positive cells in the early hypothermia group was significantly smaller than that in the normothermia group (normothermia vs early: 774,588 ± 162,173 vs 180,903 ± 42,212, p < 0.05). Also, the injury area and volume were smaller in the early hypothermia group in which hypothermia was induced before craniotomy and cerebral reperfusion (early, 115.2 ± 15.4 mm(3); late, 344.7 ± 29.1 mm(3); normothermia, 311.2 ± 79.2 mm(3); p < 0.05).

CONCLUSIONS

The data suggest that early, preoperatively induced hypothermia could mediate the reduction of neuronal and glial damage in the reperfusion phase of ischemia/reperfusion brain injury.

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.

Ex vivo rehabilitation of non-heart-beating donor lungs in preclinical porcine model: delayed perfusion results in superior lung function

OBJECTIVES

Ex vivo lung perfusion (EVLP) is a promising modality for the evaluation and treatment of marginal donor lungs. The optimal timing of EVLP initiation and the potential for rehabilitation of donor lungs with extended warm ischemic times is unknown. The present study compared the efficacy of different treatment strategies for uncontrolled non-heart-beating donor lungs.

METHODS

Mature swine underwent hypoxic arrest, followed by 60 minutes of no-touch warm ischemia. The lungs were harvested and flushed with 4°C Perfadex. Three groups (n = 5/group) were stratified according to the preservation method: cold static preservation (CSP; 4 hours of 4°C storage), immediate EVLP (I-EVLP: 4 hours EVLP at 37°C), and delayed EVLP (D-EVLP; 4 hours of CSP followed by 4 hours of EVLP). The EVLP groups were perfused with Steen solution supplemented with heparin, methylprednisolone, cefazolin, and an adenosine 2A receptor agonist. The lungs then underwent allotransplantation and 4 hours of recipient reperfusion before allograft assessment for resultant ischemia-reperfusion injury.

RESULTS

The donor blood oxygenation (partial pressure of oxygen/fraction of inspired oxygen ratio) before death was not different between the groups. The oxygenation after transplantation was significantly greater in the D-EVLP group than in the I-EVLP or CSP groups. The mean airway pressure, pulmonary artery pressure, and expression of interleukin-8, interleukin-1β, and tumor necrosis factor-α were all significantly reduced in the D-EVLP group. Post-transplant oxygenation exceeded the acceptable clinical levels only in the D-EVLP group.

CONCLUSIONS

Uncontrolled non-heart-beating donor lungs with extended warm ischemia can be reconditioned for successful transplantation. The combination of CSP and EVLP in the D-EVLP group was necessary to obtain optimal post-transplant function. This finding, if confirmed clinically, will allow expanded use of nonheart-beating donor lungs.

Ischemia/reperfusion-induced MKP-3 impairs endothelial NO formation via inactivation of ERK1/2 pathway

Mitogen-activated protein kinase phosphatases (MKPs) are a family of dual-specificity phosphatases. Endothelial cells express multiple MKP family members, such as MKP-3. However, the effects of MKP-3 on endothelial biological processes have not yet been fully elucidated. Here, we address the association between MKP-3 and endothelial Nitric oxide (NO) formation under ischemia/reperfusion (IS/RP) condition. Human umbilical vein endothelial cells (HUVECs) were subjected to IS/RP treatment. The MKP-3 expression and NO formation were examined. IS/RP induced endothelial MKP-3 expression and inhibited eNOS expression and NO formation, accompanied by an increase of endothelial apoptosis. The siRNA experiments showed that MKP-3 was an important mediator in impairing eNOS expression and NO production in endothelial cells. Transfection of HUVECs with constitutively active ERK plasmids suggested that the above mentioned effect of MKP-3 was via inactivation of ERK1/2 pathway. Furthermore, impairment of eNOS expression was restored by treatment of histone deacetylase (HDAC) inhibitor and related to histone deacetylation and recruitment of HDAC1 to the eNOS promoter. Finally, Salvianolic acid A (SalA) markedly attenuated induction of MKP-3 and inhibition of eNOS expression and NO formation under endothelial IS/RP condition. Overall, these results for the first time demonstrated that IS/RP inhibited eNOS expression by inactivation of ERK1/2 and recruitment of HDAC1 to the gene promoter, leading to decreased NO formation through a MKP-3-dependent mechanism in endothelial cells, and SalA has therapeutic significance in protecting endothelial cells from impaired NO formation in response to IS/RP.

Stress-specific responses of p21 expression: implication of transcript variant p21 alt-a in long-term hypoxia

p21 (CDKN1A, Cip1, Waf1) is a cyclin-dependent kinase inhibitor capable of causing cell cycle arrest or promoting cell cycle transit as well as acting as a regulator of apoptosis. In this study, we analyzed the effects of various antemortem conditions on p21 protein level and expression profiles of known p21 transcript variants in human heart tissue. The selected death cause groups were: non-cardiac, hypothermia, acute ischemia, and chronic hypoxia. Immunohistochemical staining of p21 in cardiac myocytes could be observed only in hypothermia death cases, in which the mRNA expression of the most abundant variant, p21V1, also exceeded that in other death cause groups. Cytoplasmic localization of p21 protein in vascular smooth muscle cells together with substantially increased expression of cardioprotective Pim-1 especially in chronic hypoxia, but in acute ischemia and hypothermia as well, indicate change of p21 function from cell cycle arrest to promotion of proliferation and cell survival in these cases. In chronic hypoxia deaths the expression of variant p21 alt-a was highly pronounced whereas the expression of variant p21B was low. In chronic hypoxia deaths the expression of p53 was substantially higher compared to the other groups, being a potential regulator of p21 alt-a expression. In acute ischemia deaths increased expression of variant p21B, suggested to be proapoptotic in several cell lines, was observed. Our results suggest a role for variant p21 alt-a in hypoxia and for variant p21B in acute myocardial ischemia. The known cardioprotective aspect of hypothermia might come from an increased p21 protein level.

Combined effect of hypothermia and caspase-2 gene deficiency on neonatal hypoxic-ischemic brain injury

INTRODUCTION

[corrected] Hypoxia-ischemia (HI) injury in term infants develops with a delay during the recovery phase, opening up a therapeutic window after the insult. Hypothermia is currently an established neuroprotective treatment in newborns with neonatal encephalopathy (NE), saving one in nine infants from developing neurological deficits. Caspase-2 is an initiator caspase, a key enzyme in the route to destruction and, therefore, theoretically a potential target for a pharmaceutical strategy to prevent HI brain damage.

METHODS

The aim of this study was to explore the neuroprotective efficacy of hypothermia in combination with caspase-2 gene deficiency using the neonatal Rice-Vannucci model of HI injury in mice.

RESULTS

HI brain injury was moderately reduced in caspase-2(-/-) mice as compared with wild-type (WT) mice. Five hours of hypothermia (33 °C ) vs. normothermia (36 °C) directly after HI provided additive protection overall (temperature P = 0.0004, caspase-2 genotype P = 0.0029), in the hippocampus and thalamus, but not in other gray matter regions or white matter. Delayed hypothermia initiated 2 h after HI in combination with caspase-2 gene deficiency reduced injury in the hippocampus, but not in other brain areas.

DISCUSSION

In conclusion, caspase-2 gene deficiency combined with hypothermia provided enhanced neuroprotection as compared with hypothermia alone.

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

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

The Use of Hypothermia Therapy in Traumatic Ischemic / Reperfusional Brain Injury: Review of the Literatures

Therapeutic mild hypothermia has been used widely in brain injury. It has evaluated in numerous clinical trials, and there is strong evidence for the use of hypothermia in treating patients with several types of ischemic / reperfusional (I/R) injuries, examples being cardiac arrest and neonatal hypoxic-ischemic encephalopathy.In spite of many basic research projects demonstrating effectiveness, therapeutic hypothermia has not been proven effective for the heterogeneous group of traumatic brain injury patients in multicenter clinical trials. In the latest clinical trial, however, researchers were able to demonstrate the significant beneficial effects of hypothermia in one specific group; patients with mass evacuated lesions. This suggested that mild therapeutic hypothermia might be effective for I/R related traumatic brain injury.In this article we have reviewed much of the previous literature concerning the mechanisms of I/R injury to the protective effects of mild therapeutic hypothermia.

Osteopontin stimulates autophagy via integrin/CD44 and p38 MAPK signaling pathways in vascular smooth muscle cells

Osteopontin (OPN) exerts pro-inflammatory effect and is associated with the development of abdominal aortic aneurysm (AAA). However, the molecular mechanism underlying this association remains obscure. In the present study, we compared gene expression profiles of AAA tissues using microarray assay, and found that OPN was the highest expressed gene (>125-fold). Furthermore, the expression of LC3 protein and autophagy-related genes including Atg4b, Beclin1/Atg6, Bnip3, and Vps34 was markedly upregulated in AAA tissues. To investigate the ability of OPN to stimulate autophagy as a potential mechanism involved in the pathogenesis of this disease, we treated vascular smooth muscle cells (SMCs) with OPN, and found that OPN significantly increased the formation of autophagosomes, expression of autophagy-related genes and cell death, whereas blocking the signal by anti-OPN antibody markedly inhibited OPN-induced autophagy and SMC death. Furthermore, inhibition of integrin/CD44 and p38 MAPK signaling pathways markedly abrogated the biological effects of OPN on SMCs. These data for the first time demonstrate that OPN sitmulates autophagy directly through integrin/CD44 and p38 MAPK-mediated pathways in SMCs. Thus, inhibition of OPN-induced autophagy might be a potential therapeutic target in the treatment of AAA disease. J. Cell. Physiol. 227: 127-135, 2012. © 2011 Wiley Periodicals, Inc.

Advanced glycation end products accelerate ischemia/reperfusion injury through receptor of advanced end product/nitrative thioredoxin inactivation in cardiac microvascular endothelial cells

The advanced glycation end products (AGEs) are associated with increased cardiac endothelial injury. However, no causative link has been established between increased AGEs and enhanced endothelial injury after ischemia/reperfusion. More importantly, the molecular mechanisms by which AGEs may increase endothelial injury remain unknown. Adult rat cardiac microvascular endothelial cells (CMECs) were isolated and incubated with AGE-modified bovine serum albumin (BSA) or BSA. After AGE-BSA or BSA preculture, CMECs were subjected to simulated ischemia (SI)/reperfusion (R). AGE-BSA increased SI/R injury as evidenced by enhanced lactate dehydrogenase release and caspase-3 activity. Moreover, AGE-BSA significantly increased SI/R-induced oxidative/nitrative stress in CMECs (as measured by increased inducible nitric oxide synthase expression, total nitric oxide production, superoxide generation, and peroxynitrite formation) and increased SI/R-induced nitrative inactivation of thioredoxin-1 (Trx-1), an essential cytoprotective molecule. Supplementation of EUK134 (peroxynitrite decomposition catalyst), human Trx-1, or soluble receptor of advanced end product (sRAGE) (a RAGE decoy) in AGE-BSA precultured cells attenuated SI/R-induced oxidative/nitrative stress, reduced SI/R-induced Trx-1 nitration, preserved Trx-1 activity, and reduced SI/R injury. Our results demonstrated that AGEs may increase SI/R-induced endothelial injury by increasing oxidative/nitrative injury and subsequent nitrative inactivation of Trx-1. Interventions blocking RAGE signaling or restoring Trx activity may be novel therapies to mitigate endothelial ischemia/reperfusion injury in the diabetic population.