Moderate hypothermia ameliorates enterocyte mitochondrial dysfunction in severe shock and reperfusion

Melatonin Attenuates Sepsis-Induced Small-Intestine Injury by Upregulating SIRT3-Mediated Oxidative-Stress Inhibition, Mitochondrial Protection, and Autophagy Induction

Melatonin reportedly alleviates sepsis-induced multi-organ injury by inducing autophagy and activating class III deacetylase Sirtuin family members (SIRT1-7). However, whether melatonin attenuates small-intestine injury along with the precise underlying mechanism remain to be elucidated. To investigate this, we employed cecal ligation and puncture (CLP)- or endotoxemia-induced sepsis mouse models and confirmed that melatonin treatment significantly prolonged the survival time of mice and ameliorated multiple-organ injury (lung/liver/kidney/small intestine) following sepsis. Melatonin partially protected the intestinal barrier function and restored SIRT1 and SIRT3 activity/protein expression in the small intestine. Mechanistically, melatonin treatment enhanced NF-κB deacetylation and subsequently reduced the inflammatory response and decreased the TNF-α, IL-6, and IL-10 serum levels; these effects were abolished by SIRT1 inhibition with the selective blocker, Ex527. Correspondingly, melatonin treatment triggered SOD2 deacetylation and increased SOD2 activity and subsequently reduced oxidative stress; this amelioration of oxidative stress by melatonin was blocked by the SIRT3-selective inhibitor, 3-TYP, and was independent of SIRT1. We confirmed this mechanistic effect in a CLP-induced sepsis model of intestinal SIRT3 conditional-knockout mice, and found that melatonin preserved mitochondrial function and induced autophagy of small-intestine epithelial cells; these effects were dependent on SIRT3 activation. This study has shown, to the best of our knowledge, for the first time that melatonin alleviates sepsis-induced small-intestine injury, at least partially, by upregulating SIRT3-mediated oxidative-stress inhibition, mitochondrial-function protection, and autophagy induction.

Regional hypothermia improves gastric microcirculatory oxygenation during hemorrhage in dogs

Mild systemic hypothermia increases gastric mucosal oxygenation (μHbO₂) during hemorrhagic shock in dogs. In the context of critical blood loss hypothermia might be fatal due to adverse side effects. Selective regional hypothermia might overcome these limitations. The aim of our study was to analyze the effects of regional gastric and oral mucosal hypothermia on μHbO₂ and perfusion (μflow). In a cross-over study six anesthetized dogs were subjected to local oral and gastric mucosal hypothermia (34°C), or maintenance of local normothermia during normovolemia and hemorrhage (-20% blood volume). Macro- and microcirculatory variables were recorded continuously. During normovolemia, local hypothermia increased gastric microcirculatory flow (μflow) without affecting oxygenation (μHbO₂) or oral microcirculation. During mild hemorrhagic shock gastric μHbO₂ decreased from 72±2% to 38±3% in the normothermic group. This was attenuated by local hypothermia, where μHbO₂ was reduced from 74±3% to 52±4%. Local perfusion, oral microcirculation and macrocirculatory variables were not affected. Selective local hypothermia improves gastric μHbO₂ during hemorrhagic shock without relevant side effects. In contrast to systemic hypothermia, regional mucosal hypothermia did not affect perfusion and oxygen supply during hemorrhage. Thus, the increased μHbO₂ during local hypothermia rather indicates reduced mucosal oxygen demand.

Protective effect of extracorporeal membrane oxygenation on intestinal mucosal injury after cardiopulmonary resuscitation in pigs

The present study aimed to explore the protective effects of extracorporeal membrane oxygenation (ECMO) on intestinal mucosal injury following cardiopulmonary resuscitation (CPR), and to assess the potential mechanisms involved. A total of 24 healthy adult domestic pigs were selected as the study subjects. A ventricular fibrillation model was induced through programmed electric stimulation. Subsequently, the animals were randomly divided into conventional CPR and CPR+ECMO groups (n=12 per group). The mortality and hemodynamic parameters of the two groups were compared. The expression levels of inflammatory cytokines in the serum and intestinal mucosa were detected by ELISAs. The intestinal mucosa was subjected to hematoxylin and eosin, and immunohistochemical staining, followed by electron microscopy, to assess the degree of apoptosis and necrosis. The animals in both groups recovered from the programmed ventricular fibrillation. In the CPR group, two animals died at 2 h and two more animals died a further 2 h later, resulting in a 33.3% mortality rate, whereas no cases of mortality were observed in the CPR+ECMO group. Compared with the animals in the CPR group, the hemodynamic parameters of the animals in the CPR+ECMO group revealed significantly improved outcomes. Multiple inflammatory factors (tumor necrosis factor α, interleukin-1 and interleukin-6), myeloperoxidase and malondialdehyde levels were decreased, whereas Na/Ca-ATPase and superoxide dismutase levels were elevated in the intestinal mucosa of animals in the CPR+ECMO group compared with those in the CPR group. Additionally, pathological staining demonstrated that the intestinal mucosa tissue in the CPR+ECMO group exhibited less apoptosis, necrosis and inflammatory cell infiltration, which was further supported by a decrease in Bax expression and an increase in Bcl-2 expression. Overall, ECMO after CPR reduced the intestinal mucosal barrier injury after spontaneous circulation recovery, and the mechanism involved decreased inflammation and apoptosis.

Hibernation-Based Approaches in the Treatment of Hemorrhagic Shock

Hemorrhagic shock is the leading cause of preventable death after trauma. Hibernation-based treatment approaches have been of increasing interest for various biomedical applications. Owing to apparent similarities in tissue perfusion and metabolic activity between severe blood loss and the hibernating state, hibernation-based approaches have also emerged for the treatment of hemorrhagic shock. Research has shown that hibernators are protected from shock-induced injury and inflammation. Utilizing the adaptive mechanisms that prevent injury in these animals may help alleviate the detrimental effects of hemorrhagic shock in non-hibernating species. This review describes hibernation-based preclinical and clinical approaches for the treatment of severe blood loss. Treatments include the delta opioid receptor agonist D-Ala-Leu-enkephalin (DADLE), the gasotransmitter hydrogen sulfide, combinations of adenosine, lidocaine, and magnesium (ALM) or D-beta-hydroxybutyrate and melatonin (BHB/M), and therapeutic hypothermia. While we focus on hemorrhagic shock, many of the described treatments may be used in other situations of hypoxia or ischemia/reperfusion injury.

Endovascular hypothermia improves post-resuscitation myocardial dysfunction by increasing mitochondrial biogenesis in a pig model of cardiac arrest

The aim of the study was to investigate the effects of endovascular hypothermia on mitochondrial biogenesis in a pig model of prolonged cardiac arrest (CA). Ventricular fibrillation was electrically induced, and animals were left untreated for 10 min; then after 6min of cardiopulmonary resuscitation (CPR), defibrillation was attempted. 25 animals that were successfully resuscitated were randomized into three groups: Sham group (SG, 5, no CA), normal temperature group (NTG, 5 for 12 h observation and 5 for 24 h observation), and endovascular hypothermia group (EHG, 5 for 12 h observation and 5 for 24 h observation). The core temperatures (T_c) in the EHG were maintained at 34 ± 0.5 °C for 6 h by an endovascular hypothermia device (Coolgard 3000), then actively increased at the speed of 0.5 °C per hour during the next 6 h to achieve a normal body temperature, while T_c were maintained at 37.5 ± 0.5 °C in the NTG. Cardiac and mitochondrial functions, the quantification of myocardial mitochondrial DNA (mtDNA), peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), nuclear respiratory factor (NRF)-1, and NRF-2 were examined. Results showed that myocardial and mitochondrial injury and dysfunction increased significantly at 12 h and 24 h after CA. Endovascular hypothermia offered a method to rapidly achieve the target temperature and provide stable target temperature management (TTM). Cardiac outcomes were improved and myocardial injuries were alleviated with endovascular hypothermia. Compared with NTG, endovascular hypothermia significantly increased mitochondrial activity and biogenesis by amplifying mitochondrial biogenesis factors' expressions, including PGC-1α, NRF-1, and NRF-2. In conclusions, endovascular hypothermia after CA alleviated myocardial and mitochondrial dysfunction, and was associated with increasing mitochondrial biogenesis.

Effect of mild hypothermia preconditioning against low temperature (4°C) induced rat liver cell injury in vitro

Bioartificial liver holds special position in the field of regenerative medicine, and cold environment at 4℃ is widely used for the short storage of both organ and liver cell for later application. However, the disadvantages of such cold storage could influence cell viability and lead to cell apoptosis in different degrees. In this study, we mainly explore the pre-protective effect of mild hypothermia against low temperature (4℃)-induced rat liver cell injury in vitro. Our results indicated that the precondition with mild hypothermia could increase cell viability, such as cell proliferation, LDH regulation and glycogen synthesis ability of liver cell. The precondition also decreased the ROS production and relieved cell apoptosis in liver cells. Compared with the model group, the mitochondrial membrane potential was restored in the mild hypothermia group, as well as the mitochondrial membrane permeability transition pore opening, indicating that the therapeutic mechanism was related to mitochondrial protection. Further analysis showed that PI3K-Akt-GSK3β signal pathway might be associated with the pre-protective effect of mild hypothermia. Thus, our study suggested that the precondition with mild hypothermia hold the protective effect for liver cell in cold environment, and further developed a novel strategy for the storage of liver seed cells, even bioartificial liver.