Mild hypothermia pretreatment protects against liver ischemia reperfusion injury via the PI3K/AKT/FOXO3a pathway

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.

FNDC5/Irisin Inhibits the Inflammatory Response and Mediates the Aerobic Exercise-Induced Improvement of Liver Injury after Myocardial Infarction

Myocardial infarction (MI) causes peripheral organ injury, in addition to cardiac dysfunction, including in the liver, which is known as cardiac hepatopathy. Aerobic exercise (AE) can effectively improve liver injury, although the mechanism and targets are currently not well established. Irisin, mainly produced by cleavage of the fibronectin type III domain-containing protein 5 (FNDC5), is a responsible for the beneficial effects of exercise training. In this study, we detected the effect of AE on MI-induced liver injury and explored the role of irisin alongside the benefits of AE. Wildtype and Fndc5 knockout mice were used to establish an MI model and subjected to AE intervention. Primary mouse hepatocytes were treated with lipopolysaccharide (LPS), rhirisin, and a phosphoinositide 3-kinase (PI3K) inhibitor. The results showed that AE significantly promoted M2 polarization of macrophages and improved MI-induced inflammation, upregulated endogenous irisin protein expression and activated the PI3K/ protein kinase B (Akt) signaling pathway in the liver of MI mice, while knockout of Fndc5 attenuated the beneficial effects of AE. Exogenous rhirisin significantly inhibited the LPS-induced inflammatory response, which was attenuated by the PI3K inhibitor. These results suggest that AE could effectively activate the FNDC5/irisin-PI3K/Akt signaling pathway, promote the polarization of M2 macrophages, and inhibit the inflammatory response of the liver after MI.

Investigating the effects of chronic low-dose radiation exposure in the liver of a hypothermic zebrafish model

Mankind's quest for a manned mission to Mars is placing increased emphasis on the development of innovative radio-protective countermeasures for long-term space travel. Hibernation confers radio-protective effects in hibernating animals, and this has led to the investigation of synthetic torpor to mitigate the deleterious effects of chronic low-dose-rate radiation exposure. Here we describe an induced torpor model we developed using the zebrafish. We explored the effects of radiation exposure on this model with a focus on the liver. Transcriptomic and behavioural analyses were performed. Radiation exposure resulted in transcriptomic perturbations in lipid metabolism and absorption, wound healing, immune response, and fibrogenic pathways. Induced torpor reduced metabolism and increased pro-survival, anti-apoptotic, and DNA repair pathways. Coupled with radiation exposure, induced torpor led to a stress response but also revealed maintenance of DNA repair mechanisms, pro-survival and anti-apoptotic signals. To further characterise our model of induced torpor, the zebrafish model was compared with hepatic transcriptomic data from hibernating grizzly bears (Ursus arctos horribilis) and active controls revealing conserved responses in gene expression associated with anti-apoptotic processes, DNA damage repair, cell survival, proliferation, and antioxidant response. Similarly, the radiation group was compared with space-flown mice revealing shared changes in lipid metabolism.

Mild hypothermia alleviates oxygen−glucose deprivation/reperfusion-induced apoptosis by inhibiting ROS generation, improving mitochondrial dysfunction and regulating DNA damage repair pathway in PC12 cells

The brain ischemia/reperfusion (I/R) injury has a great impact on human life and property safety. As far as we know, mild hypothermia (MH) is an effective measure to reduce neuronal injury after I/R. However, the precise mechanism is not extremely clear. The purpose of this study was to investigate whether mild therapeutic hypothermia can play a protective role in nerve cells dealing with brain I/R injury and explore its specific mechanism in vitro. A flow cytometer, cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release assay were performed to detect apoptotic rate of cells, cell viability and cytotoxicity, respectively, reactive oxygen species (ROS) assay kit, JC-1 fluorescent methods, immunofluorescence and western blot were used to explore ROS, mitochondrial transmembrane potential (^Δψm), mitochondrial permeability transition pore (MPTP) and protein expression, respectively. The result indicated that the cell activity was decreased, while the cytotoxicity and apoptosis rate were increased after treating with oxygen-glucose deprivation/reperfusion (OGD/R) in PC12 cells. However, MH could antagonize this phenomenon. Interestingly, treating with OGD/R increased the release of ROS and the transfer of Cytochrome C (Cyt-C) from mitochondria to cytoplasm. In addition, it up-regulated the expression of γH2AX, Bax and Clv-caspase3, down-regulated the expression of PCNA, Rad51 and Bcl-2, and inhibited the function of mitochondria in PC12 cells. Excitingly, the opposite trend was observed after MH treatment. Therefore, our results suggest that MH protects PC12 cells against OGD/R-induced injury with the mechanism of inhibiting cell apoptosis by reducing ROS production, improving mitochondrial function, reducing DNA damage, and enhancing DNA repair.

MeCP2 inhibits ischemic neuronal injury by enhancing methylation of the FOXO3a promoter to repress the SPRY2-ZEB1 axis

Methyl CpG binding protein 2 (MeCP2) is involved in nerve regeneration following ischemic stroke, but the related mechanism remains unclear. Here, we found low MeCP2 expression in hippocampal tissues. Using functional analysis, we demonstrated that MeCP2 accelerated FOXO3a methylation and subsequently inhibited its expression, thus repressing the apoptosis of neuronal cells. Mechanistically, FOXO3a could bind to the promoter region of SPRY2, consequently inducing its transcription and promoting the expression of the downstream target gene ZEB1. Altogether, our study revealed that overexpression of MeCP2 can protect mice against ischemic brain injury via disruption of the FOXO3a/SPRY2/ZEB1 signaling axis. Our results identify ectopic expression of MeCP2 as a therapeutic target in ischemic stroke.

Study on the Mechanism of Mesaconitine-Induced Hepatotoxicity in Rats Based on Metabonomics and Toxicology Network

Mesaconitine (MA), one of the main diterpenoid alkaloids in Aconitum, has a variety of pharmacological effects, such as analgesia, anti-inflammation and relaxation of rat aorta. However, MA is a highly toxic ingredient. At present, studies on its toxicity are mainly focused on the heart and central nervous system, and there are few reports on the hepatotoxic mechanism of MA. Therefore, we evaluated the effects of MA administration on liver. SD rats were randomly divided into a normal saline (NS) group, a low-dose MA group (0.8 mg/kg/day) and a high-dose MA group (1.2 mg/kg/day). After 6 days of administration, the toxicity of MA on the liver was observed. Metabolomic and network toxicology methods were combined to explore the effect of MA on the liver of SD rats and the mechanism of hepatotoxicity in this study. Through metabonomics study, the differential metabolites of MA, such as L-phenylalanine, retinyl ester, L-proline and 5-hydroxyindole acetaldehyde, were obtained, which involved amino acid metabolism, vitamin metabolism, glucose metabolism and lipid metabolism. Based on network toxicological analysis, MA can affect HIF-1 signal pathway, MAPK signal pathway, PI3K-Akt signal pathway and FoxO signal pathway by regulating ALB, AKT1, CASP3, IL2 and other targets. Western blot results showed that protein expression of HMOX1, IL2 and caspase-3 in liver significantly increased after MA administration (p < 0.05). Combined with the results of metabonomics and network toxicology, it is suggested that MA may induce hepatotoxicity by activating oxidative stress, initiating inflammatory reaction and inducing apoptosis.

Sufentanil Protects the Liver from Ischemia/Reperfusion-Induced Inflammation and Apoptosis by Inhibiting ATF4-Induced TP53BP2 Expression

Liver ischemia-reperfusion (I/R) injury is a pathological process that often occurs during liver and trauma surgery. This study aimed to investigate the protective effect and potential mechanisms of sufentanil on hepatic I/R injury. I/R rat model and hypoxic/reoxygenation (H/R)-induced buffalo rat liver (BRL)-3A cell model were established. Following pretreatment with sufentanil, the enzymatic activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in rat serum and the changes of hepatic histopathology were evaluated to track the extent of liver injury. The levels of inflammatory factors were determined with ELISA kits and RT-qPCR. The infiltration of macrophages was assessed after detecting monocyte chemoattractant protein 1 (MCP-1) and F4/80 expression. Additionally, apoptosis was measured by means of TUNEL staining, and gene expression related to apoptosis was examined using RT-qPCR and western blotting. Then, TP53BP2 was overexpressed in BRL-3A cells exposed to H/R condition to evaluate whether sufentanil defended the liver against injury by regulating TP53BP2 expression. Moreover, the potential binding site of ATF4 on the TP53BP2 promoter was analyzed using JASPAR databases and verified by chromosomal immunoprecipitation (ChIP) assay. Furthermore, TP53BP2 expression and endoplasmic reticulum stress (ERS)-related protein levels were determined after ATF4 was overexpressed in sufentanil-treated BRL-3A cells. Results revealed that sufentanil significantly improved hepatic I/R injury, decreased the levels of inflammatory factors, and alleviated hepatocyte apoptosis. Notably, upregulated TP53BP2 expression was observed in hepatic tissues, and TP53BP2 overexpression markedly reversed the protective effects of sufentanil on the inflammation and apoptosis in H/R-stimulated BRL-3A cells. Additionally, ATF4 was confirmed to combine with the TP53BP2 promoter. ATF4 upregulation attenuated the inhibitory effects of sufentanil on the expression of TP53BP2 and ERS-associated proteins. These findings demonstrated that sufentanil protects the liver from inflammation and apoptosis injury induced by I/R by inhibiting ATF4 expression and further suppressing TP53BP2 expression, suggesting a promising therapeutic candidate for the treatment of liver I/R injury.

Effects of hypothermia on inflammatory cytokine expression in rat liver following asphyxial cardiac arrest

Hypothermic treatment is known to protect against cardiac arrest (CA) and improve survival rate. However, few studies have evaluated the CA-induced liver damage and the effects of hypothermia on this damage. Therefore, the aim of the present study was to determine possible protective effects of hypothermia on the liver after asphyxial CA. Rats were subjected to a 5-min asphyxial CA followed by return of spontaneous circulation (ROSC). The body temperature was controlled at 37±0.5˚C (normothermia group) or 33±0.5˚C (hypothermia group) for 4 h after ROSC. Livers were examined at 6, 12 h, 1 and 2 days after ROSC. Histopathological examination was performed by H&E staining. Alterations in the expression levels of pro-inflammatory (TNF-α and interleukin IL-2) and anti-inflammatory cytokines (IL-4 and IL-13) were investigated by immunohistochemistry. Sinusoidal dilatation and vacuolization were observed after asphyxial CA by histopathological examination. However, these CA-induced structural alterations were prevented by hypothermia. In immunohistochemical examination, the expression levels of pro-inflammatory cytokines were reduced in the hypothermia group compared with those in the normothermia group while the expression levels of anti-inflammatory cytokines were increased in the hypothermia group compared with those in the normothermia group. In conclusion, hypothermic treatment for 4 h following asphyxial CA in rats inhibited the increase of pro-inflammatory cytokines and stimulated the expression of anti-inflammatory cytokines compared with the normothermic group. The results of the present study suggested that hypothermic treatment after asphyxial CA reduced liver damage via the regulation of inflammation.

BKM120 sensitizes BRCA-proficient triple negative breast cancer cells to olaparib through regulating FOXM1 and Exo1 expression

Poly (ADP-ribose) polymerase (PARP) inhibitors offer a significant clinical benefit for triple-negative breast cancers (TNBCs) with BRCA1/2 mutation. However, the narrow clinical indication limits the development of PARP inhibitors. Phosphoinositide 3-kinase (PI3K) inhibition sensitizes BRCA-proficient TNBC to PARP inhibition, which broadens the indication of PARP inhibitors. Previously researches have reported that PI3K inhibition induced the defect of homologous recombination (HR) mediated repair by downregulating the expression of BRCA1/2 and Rad51. However, the mechanism for their synergistic effects in the treatment of TNBC is still unclear. Herein, we focused on DNA damage, DNA single-strand breaks (SSBs) repair and DNA double-strand breaks (DSBs) repair three aspects to investigate the mechanism of dual PI3K and PARP inhibition in DNA damage response. We found that dual PI3K and PARP inhibition with BKM120 and olaparib significantly reduced the proliferation of BRCA-proficient TNBC cell lines MDA-MB-231 and MDA231-LM2. BKM120 increased cellular ROS to cause DNA oxidative damage. Olaparib resulted in concomitant gain of PARP1, forkhead box M1 (FOXM1) and Exonuclease 1 (Exo1) while inhibited the activity of PARP. BKM120 downregulated the expression of PARP1 and PARP2 to assist olaparib in blocking PARP mediated repair of DNA SSBs. Meanwhile, BKM120 inhibited the expression of BRAC1/2 and Rad51/52 to block HR mediated repair through the PI3K/Akt/NFκB/c-Myc signaling pathway and PI3K/Akt/ FOXM1/Exo1 signaling pathway. BKM120 induced HR deficiency expanded the application of olaparib to HR proficient TNBCs. Our findings proved that PI3K inhibition impaired the repair of both DNA SSBs and DNA DSBs. FOXM1 and Exo1 are novel therapeutic targets that serves important roles in DNA damage response.

Research Progress of the Application of Hypothermia in the Eye

Hypothermia is widely used in the medical field to protect organs or tissues from damage. Different research fields have different explanations of the protection mechanism of hypothermia. Hypothermia is also widely used in the field of ophthalmology, for example, in the eye bank, the preservation of corneal tissue and the preservation of the eyeball. Low temperature can also be applied to some ophthalmic diseases, such as allergic conjunctivitis, retinal ischemia, and retinal hypoxia. It is used to relieve eye symptoms or reduce tissue damage. Hypothermic techniques have important applications in ophthalmic surgery, such as corneal refractive surgery, vitrectomy surgery, and ciliary body cryotherapy for end-stage glaucoma. Hypothermia can reduce the inflammation of the cornea and protect the retinal tissue. The eyeball is a complex organ, including collagen tissue of the eyeball wall and retinal nerve tissue and retinal blood vessels. The mechanism of low temperature protecting eye tissue is complicated. It is important to understand the mechanism of hypothermia and its applications in ophthalmology. This review introduces the mechanism of hypothermia and its application in the eye banks, eye diseases (allergic conjunctivitis, retinal ischemia, and hypoxia), and eye surgeries (corneal transplant surgery, corneal refractive surgery, and vitrectomy).

Moderate Hypothermia Effectively Alleviates Acetaminophen-Induced Liver Injury With Prolonged Action Beyond Cooling

Acetaminophen (APAP) overdose accounts for the highest incidence of acute liver failure, despite the availability of an antidote i.e. N-acetylcysteine. This calls for alternative strategies to manage APAP-induced liver injury (AILI). Therapeutic hypothermia has been explored in past studies for hepatoprotection, but these phenomenal reports lack clarification of its optimal window for application, and mechanistic effects in specific AILI. Hence, we conducted an in vitro study with transforming growth factor-α transgenic mouse hepatocytes cell line, TAMH, and human liver hepatocytes cell line, L-02, where cells were conditioned with deep (25°C) or moderate (32°C) hypothermia before, during or after APAP toxicity. Cell viability was evaluated as a hallmark of cytoprotection, along with cell death. Simultaneously, cold shock proteins (CSPs) and heat shock proteins expressions were monitored; key liver functions including drug-metabolizing ability and hepatic clearance were also investigated. Herein, we demonstrated significant hepatoprotection with 24-hour moderate hypothermic conditioning during AILI and this effect sustained for at least 24 hours of rewarming. Such liver preservation was associated with a CSP—RNA-binding motif protein 3 (RBM3) as its knockdown promptly abolished the cytoprotective effects of hypothermia. With mild and reversible liver perturbations, hypothermic therapy appears promising and its RBM3 involvement deserves future exploration.

Hesperidin ameliorates liver ischemia/reperfusion injury via activation of the Akt pathway

Hesperidin (HDN) is a bioflavonoid that serves a role as an antioxidant in biological systems. However, although HDN has hydrogen radical- and hydrogen peroxide-removal activities, the role of HDN in liver ischemia/reperfusion (I/R) injury remains unknown. This study aimed to determine the role of HDN in liver I/R injury. Male C57BL/6J wild-type (WT) mice were subjected to warm partial liver I/R injury. Liver damage was evaluated by measuring serum alanine aminotransferase (ALT) levels, cytokine production, oxidative stress indicators, tissue hematoxylin-eosin staining and cell death. The Akt signaling pathway was examined to elucidate the underlying mechanisms. HDN had no effect on ALT levels and tissue damage in WT mice without liver I/R injury. However, HDN significantly ameliorated liver I/R injury as measured by serum ALT levels and necrotic tissue areas. HDN decreased malondialdehyde content, but increased the levels of superoxide dismutase, catalase, glutathione peroxidase and glutathione. In addition, HDN significantly attenuated the mRNA expression levels of TNF-α, IL-6 and IL-1β after liver I/R injury. Furthermore, HDN protected the liver against apoptosis in liver I/R injury by increasing the levels of Bcl-2 and decreasing the levels of cleaved-caspase 3. Mechanistically, the levels of phosphorylated Akt were elevated by HDN during liver I/R injury. In addition, HDN could induce Akt activation in hepatocytes in vitro. Most importantly, treatment with the Akt inhibitor LY294002 in WT mice blocked the hepatoprotective effects of HDN in liver I/R injury. In summary, the results of the present study suggested that HDN may protect against liver I/R injury through activating the Akt pathway by ameliorating liver oxidative stress, suppressing inflammation and preventing hepatocyte apoptosis. HDN may be a useful factor for liver injury protection and a potential therapeutic treatment for liver I/R injury in the future.

Mild Hypothermia Attenuates Hepatic Ischemia-Reperfusion Injury through Regulating the JAK2/STAT3-CPT1a-Dependent Fatty Acid β-Oxidation

Hepatic ischemia–reperfusion (IR) injury is a clinical issue that can result in poor outcome and lacks effective therapies at present. Mild hypothermia (32–35°C) is a physiotherapy that has been reported to significantly alleviate IR injury, while its protective effects are attributed to multiple mechanisms, one of which may be the regulation of fatty acid β-oxidation (FAO). The aim of the present study was to investigate the role and underlying mechanisms of FAO in the protective effects of mild hypothermia. We used male mice to establish the experimental models as previously described. In brief, before exposure to in situ ischemia for 1 h and reperfusion for 6 h, mice received pretreatment with mild hypothermia for 2 h and etomoxir (inhibitor of FAO) or leptin (activator of FAO) for 1 h, respectively. Then, tissue and blood samples were collected to evaluate the liver injury, oxidative stress, and changes in hepatic FAO. We found that mild hypothermia significantly reduced the hepatic enzyme levels and the score of hepatic pathological injury, hepatocyte apoptosis, oxidative stress, and mitochondrial injury. In addition, the expression of the rate-limiting enzyme (CPT1a) of hepatic FAO was downregulated almost twofold by IR, while this inhibition could be significantly reversed by mild hypothermia. Experiments with leptin and etomoxir confirmed that activation of FAO could also reduce the hepatic enzyme levels and the score of hepatic pathological injury, hepatocyte apoptosis, oxidative stress, and mitochondrial injury induced by IR, which had the similar effects to mild hypothermia, while inhibition of FAO had negative effects. Furthermore, mild hypothermia and leptin could promote the phosphorylation of JAK2/STAT3 and upregulate the ratio of BCL-2/BAX to suppress hepatocyte apoptosis. Thus, we concluded that FAO played an important role in hepatic IR injury and mild hypothermia attenuated hepatic IR injury mainly via the regulation of JAK2/STAT3-CPT1a-dependent FAO.

The Upstream Pathway of mTOR-Mediated Autophagy in Liver Diseases

Autophagy, originally found in liver experiments, is a cellular process that degrades damaged organelle or protein aggregation. This process frees cells from various stress states is a cell survival mechanism under stress stimulation. It is now known that dysregulation of autophagy can cause many liver diseases. Therefore, how to properly regulate autophagy is the key to the treatment of liver injury. mechanistic target of rapamycin (mTOR)is the core hub regulating autophagy, which is subject to different upstream signaling pathways to regulate autophagy. This review summarizes three upstream pathways of mTOR: the phosphoinositide 3-kinase (PI3K)/protein kinase (AKT) signaling pathway, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, and the rat sarcoma (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-extracellular activated protein kinase kinase (MEK)/ extracellular-signal-regulated kinase (ERK) signaling pathway, specifically explored their role in liver fibrosis, hepatitis B, non-alcoholic fatty liver, liver cancer, hepatic ischemia reperfusion and other liver diseases through the regulation of mTOR-mediated autophagy. Moreover, we also analyzed the crosstalk between these three pathways, aiming to find new targets for the treatment of human liver disease based on autophagy.

Iron overload threatens the growth of osteoblast cells via inhibiting the PI3K/AKT/FOXO3a/DUSP14 signaling pathway

Iron overload is a common stress in the development of cells. Growing evidence has indicated that iron overload is associated with osteoporosis. Therefore, enhancing the understanding of iron overload would benefit the development of novel approaches to the treatment of osteoporosis. The purpose of the present study was to analyze the effect of iron overload on osteoblast cells, via the MC3T3-E1 cell line, and to explore its possible underlying molecular mechanisms. Ferric ammonium citrate (FAC) was utilized to simulate iron overload conditions in vitro. FAC-induced iron overload strongly suppressed proliferation of osteoblast cells and induced apoptosis. Moreover, iron overload strongly suppressed the expression of dual-specificity phosphatase 14 (DUSP14). Additionally, overexpression of DUSP14 protected osteoblast cells from the deleterious effects of iron overload, and this protective effect was mediated by FOXO3a. Additionally, matrine rescued the function of DUSP14 in osteoblast cells. Most importantly, our analysis demonstrated the essential role of the PI3K/AKT/FOXO3a/DUSP14 signaling pathway in the defense against iron overload in osteoblast cells. Overall, our results not only elucidate deleterious effects of iron overload, but also unveil its possible signaling pathway in osteoblast cells.

The Role of O-GlcNAcylation for Protection against Ischemia-Reperfusion Injury

Ischemia reperfusion injury (IR injury) associated with ischemic heart disease contributes significantly to morbidity and mortality. O-linked β-N-acetylglucosamine (O-GlcNAc) is a dynamic posttranslational modification that plays an important role in numerous biological processes, both in normal cell functions and disease. O-GlcNAc increases in response to stress. This increase mediates stress tolerance and cell survival, and is protective. Increasing O-GlcNAc is protective against IR injury. Experimental cellular and animal models, and also human studies, have demonstrated that protection against IR injury by ischemic preconditioning, and the more clinically applicable remote ischemic preconditioning, is associated with increases in O-GlcNAc levels. In this review we discuss how the principal mechanisms underlying tissue protection against IR injury and the associated immediate elevation of O-GlcNAc may involve attenuation of calcium overload, attenuation of mitochondrial permeability transition pore opening, reduction of endoplasmic reticulum stress, modification of inflammatory and heat shock responses, and interference with established cardioprotective pathways. O-GlcNAcylation seems to be an inherent adaptive cytoprotective response to IR injury that is activated by mechanical conditioning strategies.

Mild hypothermia during the reperfusion phase protects mitochondrial bioenergetics against ischemia-reperfusion injury in an animal model of ex-vivo liver transplantation-an experimental study

The organ preservation paradigm has changed following the development of new ways to preserve organs. The use of machine perfusion to preserve organs appears to have several advantages compared with conventional static cold storage. For liver transplants, the temperature control provided by machine perfusion improves organ preservation. In this experimental study, we measured the effects of different temperatures on mitochondrial bioenergetics during the reperfusion phase. An experimental model of ex-vivo liver transplantation was developed in Wistar rats (Rattus norvegicus). After total hepatectomy, cold static preservation occurred at 4ºC and reperfusion was performed at 37ºC and 32ºC using a Langendorff system. We measured parameters associated with mitochondrial bioenergetics in the livers. Compared with the livers that underwent normothermic reperfusion, mild hypothermia during reperfusion caused significant increases in the mitochondrial membrane potential, the adenosine triphosphate content, and mitochondrial respiration, and a significant reduction in the lag phase (all P < 0.001). Mild hypothermia during reperfusion reduced the effect of ischemia-reperfusion injury on mitochondrial activity in liver tissue and promoted an increase in bioenergetic availability compared with normothermic reperfusion.

DHA attenuates hepatic ischemia reperfusion injury by inhibiting pyroptosis and activating PI3K/Akt pathway

Hepatic ischemia reperfusion (I/R) injury is very common in liver transplantation and major liver surgeries and may cause liver failure or even death. Docosahexaenoic acid (DHA) has displayed activities in reducing oxidative stress and inflammatory reaction in many disorders. In the present study, we investigated the protective effects of DHA against I/R-induced injury and the underlying mechanisms. Here, we show that DHA protected hepatic I/R injury by reducing aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and decreasing the oxidative stress in liver tissues. The viability of Buffalo rat liver (BRL) cells was reduced by hypoxia/restoration (H/R) but restored by DHA. DHA significantly downregulated the expression of pyroptosis-related proteins including NLR pyrin domain containing 3 (NLRP3), apoptotic speck-like protein containing CARD (ASC) and cleaved caspase-1 and reduced the secretion of pro-inflammatory cytokines. The above results were supported by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. However, incubation with LY294002, a specific inhibitor of phosphatidylinositol-3-kinase (PI3K), abolished the effects of DHA, since it increased the expression of cleaved caspase-1 and the production of inflammatory cytokines. The present results have demonstrated that DHA ameliorated I/R-induced injury by inhibiting pyroptosis of hepatocytes induced in liver I/R injury in vivo and in vitro through the PI3K/Akt pathway, providing a potential therapeutic option to prevent liver injury by I/R.