Hypothermia can reverse hepatic oxidative stress damage induced by hypoxia in rats

Therapeutic Hypothermia Inhibits Hypoxia-Induced Cardiomyocyte Apoptosis Via the MiR-483-3p/Cdk9 Axis

Background Therapeutic hypothermia has a beneficial effect on cardiac function after acute myocardial infarction, but the exact mechanism is still unclear. Recent research has suggested that microRNAs participate in acute myocardial infarction to regulate cardiomyocyte survival. This study aimed to explore the ability of hypothermia-regulated microRNA-483-3p (miR-483-3p) to inhibit hypoxia-induced myocardial infarction. Methods and Results Primary cardiomyocytes were cultured under hypoxia at 32 °C to mimic therapeutic hypothermia, and the differentially expressed microRNAs were determined by RNA sequencing. Therapeutic hypothermia recovered hypoxia-induced increases in apoptosis, decreases in ATP levels, and decreases in miR-483-3p expression. Overexpression of miR-483-3p exhibited effects similar to those of therapeutic hypothermia on hypoxia in the treatment of cardiomyocytes to associate with maintaining the mitochondrial membrane potential, and cyclin-dependent kinase 9 (Cdk9) was identified as a target gene with downregulated expression by miR-483-3p. Knockdown of Cdk9 also promoted cardiac survival, ATP production, and mitochondrial membrane potential stability under hypoxia. In vivo, the expression of miR-483-3p and Cdk9 was tested in the cardiac tissue of the mice with acute myocardial infarction, and the expression of miR-483-3p decreased and Cdk9 increased in the region of myocardial infarction. However, miR-483-3p was overexpressed with lentivirus, which suppressed apoptosis, infarct size (miR-483-3p, 22.00±4.04% versus negative control, 28.57±5.44%, P<0.05), and Cdk9 expression to improve cardiac contractility. Conclusions MiR-483-3p antagonizes hypoxia, leading to cardiomyocyte injury by targeting Cdk9, which is a new mechanism of therapeutic hypothermia.

Protective effect of Salidroside on hypoxia-related liver oxidative stress and inflammation via Nrf2 and JAK2/STAT3 signaling pathways

High-altitude hypoxia-induced oxidative stress and inflammation played an essential role in the incidence and development of liver injury. Salidroside (Sal), a phenylpropanoid glycoside extracted from the plant Rhodiola rosea, has recently demonstrated antioxidant, anti-inflammatory, and antihypoxia properties. Herein, we hypothesized that salidroside may alleviate hypoxia-induced liver injury via antioxidant and antiinflammatory-related pathways. A high-altitude hypoxia animal model was established using hypobaric chamber. Male SD rats were randomly divided into the control group, hypoxia group, control +Sal group, and hypoxia +Sal group. Salidroside treatment significantly inhibited hypoxia-induced increases of serum and hepatic pro-inflammatory cytokines release, hepatic ROS production and MDA contents; attenuated hypoxia-induced decrease of hepatic SOD, CAT, and GSH-Px activities. Furthermore, salidroside treatment also potentiated the activation of Nrf2-mediated anti-oxidant pathway, as indicated by upregulation of n-Nrf2 and its downstream HO-1 and NQO-1. In vitro study found that blocking the Nrf2 pathway using specific inhibitor ML385 significantly reversed the protective effect of salidroside on hypoxia-induced liver oxidative stress. In addition, salidroside treatment significantly inhibited hepatic pro-inflammatory cytokines release via JAK2/STAT3-mediated pathway. Taken together, our findings suggested that salidroside protected against hypoxia-induced hepatic oxidative stress and inflammation via Nrf2 and JAK2/STAT3 signaling pathways.

Effects of Therapeutic Hypothermia on Normal and Ischemic Heart

Therapeutic hypothermia has been used for treating brain injury after out-of-hospital cardiac arrest. Its potential benefit on minimizing myocardial ischemic injury has been explored, but clinical evidence has yet to confirm positive results in preclinical studies. Importantly, therapeutic hypothermia for myocardial infarction is unique in that it can be initiated prior to reperfusion, in contrast to its application for brain injury in resuscitated cardiac arrest patients. Recent advance in cooling technology allows more rapid cooling of the heart than ever and new clinical trials are designed to examine the efficacy of rapid therapeutic hypothermia for myocardial infarction. In this review, we summarize current knowledge regarding the effect of hypothermia on normal and ischemic hearts and discuss issues to be solved in order to realize its clinical application for treating acute myocardial infarction.

Therapeutic hypothermia reduces inflammation and oxidative stress in the liver after asphyxial cardiac arrest in rats

BACKGROUND

Few studies have evaluated the effects of hypothermia on cardiac arrest (CA)-induced liver damage. This study aimed to investigate the effects of hypothermic therapy on the liver in a rat model of asphyxial cardiac arrest (ACA).

METHODS

Rats were subjected to 5-minute ACA followed by return of spontaneous circulation (RoSC). Body temperature was controlled at 33°C±0.5°C or 37°C±0.5°C for 4 hours after RoSC in the hypothermia group and normothermia group, respectively. Liver tissues in each group were collected at 6 hours, 12 hours, 1 day, and 2 days after RoSC. To examine hepatic inflammation, mast cells were stained with toluidine blue. Superoxide anion radical production was evaluated using dihydroethidium fluorescence straining and expression of endogenous antioxidants (superoxide dismutase 1 [SOD1] and SOD2) was examined using immunohistochemistry.

RESULTS

There were significantly more mast cells in the livers of the normothermia group with ACA than in the hypothermia group with ACA. Gradual increase in superoxide anion radical production was found with time in the normothermia group with ACA, but production was significantly suppressed in the hypothermia group with ACA relative to the normothermia group with ACA. SOD1 and SOD2 levels were higher in the hypothermia group with ACA than in the normothermia group with ACA.

CONCLUSIONS

Experimental hypothermic treatment after ACA significantly inhibited inflammation and superoxide anion radical production in the rat liver, indicating that this treatment enhanced or maintained expression of antioxidants. Our findings suggest that hypothermic therapy after CA can reduce mast cell-mediated inflammation through regulation of oxidative stress and the expression of antioxidants in the liver.

Advanced oxidation protein products play critical roles in liver diseases

There is a complex oxidant and antioxidant system that maintains the redox homoeostasis in the liver. While suffering from exogenous or endogenous risk factors, the balance between oxidants and antioxidants is disturbed and excessive reactive oxygen species are generated, resulting in oxidative stress. Oxidative stress is prevalent in various liver diseases and is thought to be involved in their pathophysiology. Advanced oxidation protein products are generated under conditions of oxidative damage and are newly described protein markers of oxidative stress. Previous studies have underscored the universal pathogenic roles of oxidation protein products in various diseases. However, investigations into how these products participate in the development of liver diseases have been superficial and insufficient. In this review, we highlight the current understanding of the roles of advanced oxidation protein products in liver disease pathogenesis and the underlying mechanisms. Moreover, we summarize the current studies on advanced oxidation protein products in infectious and noninfectious, acute and chronic liver diseases. Different strategies for targeting these advanced oxidation protein products and future perspectives, which may pave the way for developing new therapeutic strategies, will also be discussed here.

Redox Challenge in a Cultured Temperate Marine Species During Low Temperature and Temperature Recovery

Aquaculture is a growing industry that is increasingly providing a sizable proportion of fishery products for human consumption. Dietary energy and temperature fluctuations affect fish health and may even trigger mortality, causing great losses in fish production during winter. To better understand this unproductive winter period in aquaculture, the redox status in a cultured marine species, the gilthead sea bream, was analyzed for the first time by inducing controlled temperature fluctuations and reducing dietary lipid content. Two groups of fish (by triplicate), differing in their dietary lipid content (18% vs. 14%), were subjected to 30 days at 22°C (Pre-Cold), 50 days at 14°C (Cold) and then 35 days at 22°C (Recovery). Plasma and liver redox metabolites (oxidized lipid, oxidized protein and thiol groups), liver glutathione forms (total, oxidized and reduced) and liver antioxidant enzyme activities were measured. Reducing dietary lipid content did not affect gilthead sea bream growth, glutathione levels or enzyme activities, but did reduce the amount of oxidized lipids. A sustained low temperature of 14°C showed a lack of adaptation of antioxidant enzyme activities, mainly catalase and glutathione reductase, which subsequently affected the glutathione redox cycle and caused an acute reduction in total hepatic glutathione levels, irrespective of diet. Antioxidant enzyme activities were gradually restored to their pre-cold levels, but the glutathione redox cycle was not restored to its pre-cold values during the recovery period used. Moreover, the lower lipid diet was associated with transiently increased liver oxidized protein levels. Thus, we propose that fish should be fed a low lipid diet during pre-cold and cold periods, which would reduce oxidized lipid levels without affecting fish growth, and a higher energy diet during the recovery period. Moreover, diets supplemented with antioxidants should be considered, especially during temperature recovery.