Ischemia-Reperfusion Injury in Aged Livers-The Energy Metabolism, Inflammatory Response, and Autophagy

Impact of aging on peribiliary glands in ischemia-reperfusion injury

BACKGROUND

The detailed mechanisms underlying the development of ischemia-type biliary lesions (ITBLs) in aged donor grafts remain unclear. In the present study we aimed to investigate the impact of aging on the response of the peribiliary gland (PBG) to ischemia-reperfusion injury (IRI) and its temporal changes.

METHODS

Experiments were performed using a 90-min partial warm liver ischemia model in male Wistar rats of two age groups: young (7-8 weeks old) and old (52-60 weeks old). Liver tissues were obtained 24, 72, and 168 h after IRI. Histopathological and immunohistochemical assessments of the perihilar bile duct (PHBD), including the PBG, distal to the clip-clamped site were performed.

RESULTS

Young rats showed little change in the bile duct tissues after IRI. However, old rats showed an increased PBG volume in the PHBD and marked PBG cell proliferation 24 h after IRI. Bile duct wall thickening with narrowing of the lumen peaked 72 h after IRI. Mucus production and oxidative stress in the PBG were significantly higher in old than in young rats after IRI. These findings showed a trend toward improvement 168 h after IRI.

CONCLUSION

Age-dependent differences in the response of the PBG to IRI may be related to differences in ITBL frequency.

Oridonin attenuates liver ischemia-reperfusion injury by suppressing PKM2/NLRP3-mediated macrophage pyroptosis

BACKGROUND

The NOD-like receptor protein 3 (NLRP3) mediated pyroptosis of macrophages is closely associated with liver ischemia reperfusion injury (IRI). As a covalent inhibitor of NLRP3, Oridonin (Ori), has strong anti-inflammasome effect, but its effect and mechanisms for liver IRI are still unknown.

METHODS

Mice and liver macrophages were treated with Ori, respectively. Co-IP and LC-MS/MS analysis of the interaction between PKM2 and NLRP3 in macrophages. Liver damage was detected using H&E staining. Pyroptosis was detected by WB, TEM, and ELISA.

RESULTS

Ori ameliorated liver macrophage pyroptosis and liver IRI. Mechanistically, Ori inhibited the interaction between pyruvate kinase M2 isoform (PKM2) and NLRP3 in hypoxia/reoxygenation（H/R）-induced macrophages, while the inhibition of PKM2/NLRP3 reduced liver macrophage pyroptosis and liver IRI.

CONCLUSION

Ori exerted protective effects on liver IRI via suppressing PKM2/NLRP3-mediated liver macrophage pyroptosis, which might become a potential therapeutic target in the clinic.

Cellular and molecular mechanisms of hepatic ischemia-reperfusion injury: The role of oxidative stress and therapeutic approaches

Ischemia-reperfusion (IR) or reoxygenation injury is the paradoxical exacerbation of cellular impairment following restoration of blood flow after a period of ischemia during surgical procedures or other conditions. Acute interruption of blood supply to the liver and subsequent reperfusion can result in hepatocyte injury, apoptosis, and necrosis. Since the liver requires a continuous supply of oxygen for many biochemical reactions, any obstruction of blood flow can rapidly lead to hepatic hypoxia, which could quickly progress to absolute anoxia. Reoxygenation results in the increased generation of reactive oxygen species and oxidative stress, which lead to the enhanced production of proinflammatory cytokines, chemokines, and other signaling molecules. Consequent acute inflammatory cascades lead to significant impairment of hepatocytes and nonparenchymal cells. Furthermore, the expression of several vascular growth factors results in the heterogeneous closure of numerous hepatic sinusoids, which leads to reduced oxygen supply in certain areas of the liver even after reperfusion. Therefore, it is vital to identify appropriate therapeutic modalities to mitigate hepatic IR injury and subsequent tissue damage. This review covers all the major aspects of cellular and molecular mechanisms underlying the pathogenesis of hepatic ischemia-reperfusion injury, with special emphasis on oxidative stress, associated inflammation and complications, and prospective therapeutic approaches.

Effects of remote ischemic preconditioning in hepatectomy: a systematic review and meta-analysis

BACKGROUND

Animal experiments have confirmed that remote ischemic preconditioning (RIPC) can reduce hepatic ischemia-reperfusion injuries (HIRIs), significantly improving early tissue perfusion and oxygenation of the residual liver after resections, accelerating surgical prognoses, and improving survival rates. However, there is still controversy over the role of RIPC in relieving HIRI in clinical studies, which warrants clarification. This study aimed to evaluate the beneficial effects and applicability of RIPC in hepatectomy and to provide evidence-based information for clinical decision-making.

METHODS

Randomized controlled trials (RCTs) evaluating the efficacy and safety of RIPC interventions were collected, comparing RIPC to no preconditioning in patients undergoing hepatectomies. This search spanned from database inception to January 2024. Data were extracted independently by two researchers according to the PRISMA guidelines. The primary outcomes assessed were postoperative alanine transaminase (ALT), aspartate transaminase (AST), total bilirubin (TBIL), and albumin (ALB) levels. The secondary outcomes assessed included duration of surgery and Pringle, length of postoperative hospital stay, intraoperative blood loss and transfusion, indocyanine green (ICG) clearance, hepatocyte apoptosis index, postoperative complications, and others.

RESULTS

Ten RCTs were included in this meta-analysis, with a total of 865 patients (428 in the RIPC group and 437 in the control group). ALT levels in the RIPC group were lower than those in the control group on postoperative day (POD) 1 (WMD = - 59.24, 95% CI: - 115.04 to - 3.45; P = 0.04) and POD 3 (WMD = - 27.47, 95% CI: - 52.26 to - 2.68; P = 0.03). However, heterogeneities were significant (I2 = 89% and I2 = 78%), and ALT levels on POD 3 were unstable based on a sensitivity analysis. AST levels on POD 1 in the RIPC group were lower than those in the control group (WMD = - 50.03, 95% CI: - 94.35 to - 5.71; P = 0.03), but heterogeneity was also significant (I2 = 81%). A subgroup analysis showed no significant differences in ALT and AST levels on POD 1 between groups, regardless of whether the Pringle maneuver or propofol was used for anesthesia (induction only or induction and maintenance, P > 0.05). The remaining outcome indicators were not statistically significant or could not be analyzed due to lack of sufficient data.

CONCLUSION

RIPC has some short-term liver protective effects on HIRIs during hepatectomies. However, there is still insufficient evidence to encourage its routine use to improve clinical outcomes.

TRIAL REGISTRATION

The protocol of this study was registered with PROSPERO (CRD42022333383).

The impact of postoperative complications on oncological outcomes of liver transplantation for hepatocellular carcinoma: A competing risk analysis

OBJECTIVE

To investigate the influence of postoperative complications on tumor-related (TRD), disease-free survival (DFS) and overall survival (OS) in patients undergoing liver transplant (LT) for hepatocellular carcinoma (HCC).

METHODS

We retrospectively evaluated 425 LTs for HCC from 2010 to 2019. Postoperative complications were classified according to Comprehensive Complication Index (CCI) and the posttransplant risk of TRD assessed through Metroticket 2.0 calculator. The population was stratified into high-risk and low-risk cohorts based on the predicted TRD risk of 80%. In a second step, we re-evaluated TRD, DFS and OS of both cohorts according to a further stratification based on 47.3 points of CCI cut-off.

RESULTS

In the low-risk cohort, we observed a significantly better DFS (84% vs. 46%, p<0.001), TRD (3% vs. 26%, p<0.001) and OS (89% vs. 62%, p<0.001) in the group with CCI < 47.3. In the high-risk cohort, patients with CCI < 47.3 had significantly better DFS (50% vs. 23%, p = 0.003) and OS (68% vs. 42%, p = 0.02) and a comparable TRD (22% vs. 31%, p = 0.142).

CONCLUSIONS

A complicated postoperative course negatively influenced long-term survival. This poorer oncological outcome associated with in-hospital postoperative complications suggests that every effort should be made to improve the early posttransplant course in HCC patients, including a careful donor-to recipient match and use of new perfusion technologies.

Transcriptomics and metabolomics study in mouse kidney of the molecular mechanism underlying energy metabolism response to hypoxic stress in highland areas

Exposure to hypoxia disrupts energy metabolism and induces inflammation. However, the pathways and mechanisms underlying energy metabolism disorders caused by hypoxic conditions remain unclear. In the present study, a hypoxic animal model was created and transcriptomic and non-targeted metabolomics techniques were applied to further investigate the pathways and mechanisms of hypoxia exposure that disrupt energy metabolism. Transcriptome results showed that 3,007 genes were significantly differentially expressed under hypoxic exposure, and Gene Ontology annotation analysis and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis showed that the differentially expressed genes (DEGs) were mainly involved in energy metabolism and were significantly enriched in the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) pathway. The DEGs IDH3A, SUCLA2, and MDH2 in the TCA cycle and the DEGs NDUFA3, NDUFS7, UQCRC1, CYC1 and UQCRFS1 in the OXPHOS pathway were validated using mRNA and protein expression, and the results showed downregulation. The results of non-targeted metabolomics showed that 365 significant differential metabolites were identified under plateau hypoxia stress. KEGG enrichment analysis showed that the differential metabolites were mainly enriched in metabolic processes, such as energy, nucleotide and amino acid metabolism. Hypoxia exposure disrupted the TCA cycle and reduced the synthesis of amino acids and nucleotides by decreasing the concentration of cis-aconitate, α-ketoglutarate, NADH, NADPH and that of most amino acids, purines, and pyrimidines. Bioinformatics analysis was used to identify inflammatory genes related to hypoxia exposure and some of them were selected for verification. It was shown that the mRNA and protein expression levels of IL1B, IL12B, S100A8 and S100A9 in kidney tissues were upregulated under hypoxic exposure. The results suggest that hypoxia exposure inhibits the TCA cycle and the OXPHOS signalling pathway by inhibiting IDH3A, SUCLA2, MDH2, NDUFFA3, NDUFS7, UQCRC1, CYC1 and UQCRFS1, thereby suppressing energy metabolism, inducing amino acid and nucleotide deficiency and promoting inflammation, ultimately leading to kidney damage.

Hepatic ischemia-reperfusion syndrome and its effect on the cardiovascular system: The role of treprostinil, a synthetic prostacyclin analog

Hepatic ischemia-reperfusion syndrome has been the subject of intensive study and experimentation in recent decades since it is responsible for the outcome of several clinical entities, such as major hepatic resections and liver transplantation. In addition to the organ's post reperfusion injury, this syndrome appears to play a central role in the dysfunction of distant tissues and systems. Thus, continuous research should be directed toward finding effective therapeutic options to improve the outcome and reduce the postoperative morbidity and mortality rates. Treprostinil is a synthetic analog of prostaglandin I2, and its experimental administration has shown encouraging results. It has already been approved by the Food and Drug Administration in the United States for pulmonary arterial hypertension and has been used in liver transplantation, where preliminary encouraging results showed its safety and feasibility by using continuous intravenous administration at a dose of 5 ng/kg/min. Treprostinil improves renal and hepatic function, diminishes hepatic oxidative stress and lipid peroxidation, reduces hepatictoll-like receptor 9 and inflammation, inhibits hepatic apoptosis and restores hepatic adenosine triphosphate (ATP) levels and ATP synthases, which is necessary for functional maintenance of mitochondria. Treprostinil exhibits vasodilatory properties and antiplatelet activity and regulates proinflammatory cytokines; therefore, it can potentially minimize ischemia-reperfusion injury. Additionally, it may have beneficial effects on cardiovascular parameters, and much current research interest is concentrated on this compound.

Unveiling the Crucial Roles of O2•- and ATP in Hepatic Ischemia-Reperfusion Injury Using Dual-Color/Reversible Fluorescence Imaging

Hepatic ischemia-reperfusion injury (HIRI) is mainly responsible for morbidity or death due to graft rejection after liver transplantation. During HIRI, superoxide anion (O2•-) and adenosine-5'-triphosphate (ATP) have been identified as pivotal biomarkers associated with oxidative stress and energy metabolism, respectively. However, how the temporal and spatial fluctuations of O2•- and ATP coordinate changes in HIRI and particularly how they synergistically regulate each other in the pathological mechanism of HIRI remains unclear. Herein, we rationally designed and successfully synthesized a dual-color and dual-reversible molecular fluorescent probe (UDP) for dynamic and simultaneous visualization of O2•- and ATP in real-time, and uncovered their interrelationship and synergy in HIRI. UDP featured excellent sensitivity, selectivity, and reversibility in response to O2•- and ATP, which rendered UDP suitable for detecting O2•- and ATP and generating independent responses in the blue and red fluorescence channels without spectral crosstalk. Notably, in situ imaging with UDP revealed for the first time synchronous O2•- bursts and ATP depletion in hepatocytes and mouse livers during the process of HIRI. Surprisingly, a slight increase in ATP was observed during reperfusion. More importantly, intracellular O2•-─succinate dehydrogenase (SDH)─mitochondrial (Mito) reduced nicotinamide adenine dinucleotide (NADH)─Mito ATP─intracellular ATP cascade signaling pathway in the HIRI process was unveiled which illustrated the correlation between O2•- and ATP for the first time. This research confirms the potential of UDP for the dynamic monitoring of HIRI and provides a clear illustration of HIRI pathogenesis.

Evaluating the outcomes of donor-recipient age differences in young adults undergoing liver transplantation

The current liver allocation system may be disadvantaging younger adult recipients as it does not incorporate the donor-recipient age difference. Given the longer life expectancy of younger recipients, the influences of older donor grafts on their long-term prognosis should be elucidated. This study sought to reveal the long-term prognostic influence of the donor-recipient age difference in young adult recipients. Adult patients who received initial liver transplants from deceased donors between 2002 and 2021 were identified from the UNOS database. Young recipients (patients 45 years old or below) were categorized into 4 groups: donor age younger than the recipient, 0-9 years older, 10-19 years older, or 20 years older or above. Older recipients were defined as patients 65 years old or above. To examine the influence of the age difference in long-term survivors, conditional graft survival analysis was conducted on both younger and older recipients. Among 91,952 transplant recipients, 15,170 patients were 45 years old or below (16.5%); these were categorized into 6,114 (40.3%), 3,315 (21.9%), 2,970 (19.6%), and 2,771 (18.3%) for groups 1-4, respectively. Group 1 demonstrated the highest probability of survival, followed by groups 2, 3, and 4 for the actual graft survival and conditional graft survival analyses. In younger recipients who survived at least 5 years post-transplant, inferior long-term survival was observed when there was an age difference of 10 years or above (86.9% vs. 80.6%, log-rank p <0.01), whereas there was no difference in older recipients (72.6% vs. 74.2%, log-rank p =0.89). In younger patients who are not in emergent need of a transplant, preferential allocation of younger aged donor offers would optimize organ utility by increasing postoperative graft survival time.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury

Aged livers have shown aggravated liver ischemia and reperfusion (IR) injury. Timely efferocytosis of apoptotic cells is a key mechanism for avoiding excessive inflammation and tissue injury. Here, we investigated the alteration of efferocytosis by aged macrophages and its role in regulating macrophage STING (stimulator of interferon genes) signaling and liver IR injury. Aged and young mice were subjected to liver partial IR model. Liver injury and inflammation were measured. Efferocytosis by aged macrophages and the underlying regulatory mechanism were analyzed as well. Aged macrophages exhibited impaired efferocytosis with decreased MerTK (c-mer proto-oncogene tyrosine kinase) activation, which was reversed by treatment of the MerTK CRISPR activation plasmid. Increased MerTK cleavage by ADAM17 (a disintegrin and metalloproteinase 17) due to enhanced ROS (reactive oxygen species) levels contributed to defective efferocytosis by aged macrophages. MerTK activation by suppressing ADAM17 or ROS improved aged macrophage efferocytosis, leading to reduced inflammatory liver injury. Moreover, increased apoptotic hepatocytes, DNA accumulation, and macrophage STING activation were observed in aged ischemic livers. Improvement in efferocytosis by aged macrophages via MerTK activation suppressed STING activation and inflammatory liver injury. Our study demonstrates that aging suppresses MerTK- mediated macrophage efferocytosis to promote macrophage STING activation and inflammatory liver IR injury, suggesting a new mechanism and potential therapy to promote inflammation resolution and efferocytosis in aged livers.

m6A epitranscriptomic regulation of tissue homeostasis during primate aging

How N⁶-methyladenosine (m⁶A), the most abundant mRNA modification, contributes to primate tissue homeostasis and physiological aging remains elusive. Here, we characterize the m⁶A epitranscriptome across the liver, heart and skeletal muscle in young and old nonhuman primates. Our data reveal a positive correlation between m⁶A modifications and gene expression homeostasis across tissues as well as tissue-type-specific aging-associated m⁶A dynamics. Among these tissues, skeletal muscle is the most susceptible to m⁶A loss in aging and shows a reduction in the m⁶A methyltransferase METTL3. We further show that METTL3 deficiency in human pluripotent stem cell-derived myotubes leads to senescence and apoptosis, and identify NPNT as a key element downstream of METTL3 involved in myotube homeostasis, whose expression and m⁶A levels are both decreased in senescent myotubes. Our study provides a resource for elucidating m⁶A-mediated mechanisms of tissue aging and reveals a METTL3-m⁶A-NPNT axis counteracting aging-associated skeletal muscle degeneration.

Preservation of Mitochondrial Health in Liver Ischemia/Reperfusion Injury

Liver ischemia-reperfusion injury (LIRI) is a major cause of the development of complications in different clinical settings such as liver resection and liver transplantation. Damage arising from LIRI is a major risk factor for early graft rejection and is associated with higher morbidity and mortality after surgery. Although the mechanisms leading to the injury of parenchymal and non-parenchymal liver cells are not yet fully understood, mitochondrial dysfunction is recognized as a hallmark of LIRI that exacerbates cellular injury. Mitochondria play a major role in glucose metabolism, energy production, reactive oxygen species (ROS) signaling, calcium homeostasis and cell death. The diverse roles of mitochondria make it essential to preserve mitochondrial health in order to maintain cellular activity and liver integrity during liver ischemia/reperfusion (I/R). A growing body of studies suggest that protecting mitochondria by regulating mitochondrial biogenesis, fission/fusion and mitophagy during liver I/R ameliorates LIRI. Targeting mitochondria in conditions that exacerbate mitochondrial dysfunction, such as steatosis and aging, has been successful in decreasing their susceptibility to LIRI. Studying mitochondrial dysfunction will help understand the underlying mechanisms of cellular damage during LIRI which is important for the development of new therapeutic strategies aimed at improving patient outcomes. In this review, we highlight the progress made in recent years regarding the role of mitochondria in liver I/R and discuss the impact of liver conditions on LIRI.

Identify Key Genes Correlated to Ischemia-Reperfusion Injury in Aging Livers

Background

With the intensification of population aging, the proportion of aging livers in the donor pool is increasing rapidly. Compared with young livers, aging livers are more susceptible to ischemia-reperfusion injury (IRI) during liver transplantation, which greatly affects the utilization rate of aging livers. The potential risk factors associated with IRI in aging livers have not been fully elucidated.

Methods

In this work, five human liver tissue expression profiling datasets (GSE61260, GSE107037, GSE89632, GSE133815, and GSE151648) and a total of 28 young and aging liver tissues of human (N = 20) and mouse (N = 8) were used to screen and verify the potential risk factors associated with aging livers being more prone to IRI. DrugBank Online was used to screen drugs with potential to alleviate IRI in aging livers.

Results

The gene expression profile and immune cell composition between young and aging livers had significant differences. Among the differentially expressed genes, aryl hydrocarbon receptor nuclear translocator-like (ARNTL), BTG antiproliferation factor 2 (BTG2), C-X-C motif chemokine ligand 10 (CXCL10), chitinase 3-like 1 (CHI3L1), immediate early response 3 (IER3), Fos proto-oncogene, AP-1 transcription factor subunit (FOS), and peroxisome proliferative activated receptor, gamma, coactivator 1 alpha (PPARGC1A), mainly involved in the regulation of cell proliferation, metabolism, and inflammation, were also dysregulated in liver tissues suffered from IRI and could form a FOS-centered interaction network. Nadroparin was screened out with the potential to target FOS in DrugBank Online. In addition, the proportion of dendritic cells (DCs) was significantly upregulated in aging livers.

Conclusions

We combined the expression profiling datasets of liver tissues and samples collected in our hospital for the first time to reveal that the changes in the expression of ARNTL, BTG2, CXCL10, CHI3L1, IER3, FOS, and PPARGC1A and the proportion of dendritic cells may be associated with aging livers being more prone to IRI. Nadroparin may be used to mitigate IRI in aging livers by targeting FOS, and regulation of DC activity may also reduce IRI.

Ex Vivo Liver Machine Perfusion: Comprehensive Review of Common Animal Models

The most common preservation technique for liver grafts is static cold storage. Due to the organ shortage for liver transplantation (LT), extended criteria donor (ECD) allografts are increasingly used-despite the higher risk of inferior outcome after transplantation. Ex vivo liver machine perfusion (MP) has been developed to improve the outcome of transplantation, especially with ECD grafts, and is currently under evaluation in clinical trials. We performed a literature search on PubMed and ISI Web of Science to assemble an overview of rodent and porcine animal models of ex vivo liver MP for transplantation, which is essential for the present and future development of clinical liver MP. Hypothermic, subnormothermic, and normothermic MP systems have been successfully used for rat and pig LT. In comparison with hypothermic systems, normothermic perfusion often incorporates a dialysis unit. Moreover, it enables metabolic assessment of liver grafts. Allografts experiencing warm ischemic time have a superior survival rate after MP compared with cold storage alone, irrespective of the temperature used for perfusion. Furthermore, ex vivo MP improves the outcome of regular and ECD liver grafts in animal models. Small and large animal models of ex vivo liver MP are available to foster the further development of this new technology. Impact Statement Ex vivo machine perfusion is an important part of current research in the field of liver transplantation. While evidence for improve storage is constantly rising, the development of future applications such as quality assessment and therapeutic interventions necessitates robust animal models. This review is intended to provide an overview of this technology in common large and small animal models and to give an outlook on future applications. Moreover, we describe developmental steps that can be followed by others, and which can help to decrease the number of animals used for experiments based on the replace, reduce, refine concept.

Sodium Hydrosulfide Modification of Mesenchymal Stem Cell-Exosomes Improves Liver Function in CCL4-Induced Hepatic Injury in Mice

Background

Liver diseases and injuries are important medical problems worldwide. Acute liver failure (ALF) is a clinical syndrome characterized by severe functional impairment and widespread death of hepatocytes. Liver transplantation is the only treatment available so far. Exosomes are nanovesicles originating from intracellular organelles. They regulate the cellular and molecular mechanisms of their recipient cells and have promising potential for clinical application in acute and chronic liver injuries. This study compares the effect of Sodium hydrosulfide (NaHS) modified exosomes with non-modified exosomes in CCL4-induced acute liver injury to ascertain their role in ameliorating hepatic injury.

Methods

Human Mesenchymal stem cells (MSCs) were treated with or without NaHS (1 μmol) and exosomes were isolated using an exosome isolation kit. Male mice (8-12 weeks old) were randomly divided into four groups (n=6): 1-control, 2-PBS, 3- MSC-Exo, and 4- H2S-Exo. Animals received 2.8 ml/kg body weight of CCL4 solution intraperitoneally, and 24 h later MSC-Exo (non-modified), H2S-Exo (NaHS-modified), or PBS, was injected in the tail vein. Moreover, 24 h after Exo administration, mice were sacrificed for tissue and blood collection.

Results

Administration of both MSC-Exo and H2S-Exo reduced inflammatory cytokines (IL-6, TNF-α), total oxidant levels, liver aminotransferases, and cellular apoptosis.

Conclusion

MSC-Exo and H2S-Exo had hepato-protective effects against CCL4-induced liver injury in mice. Modification of cell culture medium with NaHS as an H2S donor enhances the therapeutic effects of MSC exosomes.

The hepato-protective effect of H2S-modified and non-modified mesenchymal stem cell exosomes on liver ischemia-reperfusion injury in mice: The role of MALAT1

INTRODUCTION

Ischemia-reperfusion injury (IRI) by causing histopathological changes is considered one of the most important causes of liver failure and dysfunction after surgery which affect graft outcomes. Stem cells are new promising approaches to treating different diseases. One of the critical strategies to improve their function is the preconditioning of their culture medium. This study compared the effect of NaHS-modified and non-modified mesenchymal stem cell exosomes on liver ischemia-reperfusion injury in mice.

METHODS

Human umbilical cord-derived MSC (MSC) cultured in a 75 cm3 flask and when confluency reached about 80%, the culture medium replaced with a serum-free medium, and 48 h later supernatants collected, concentrated, and then MSC-Exo extracted. To obtain H2S-Exo, MSC was treated with NaHS (1 μmol),the supernatant collected after 48 h, concentrated and exosomes extracted. Twenty-four male mice were randomly divided into four groups (n = 6) including: 1-ischemia, 2-sham-operated, 3- MSC-Exo, and 4- H2S-Exo. To induce ischemia, the hepatic artery and portal vein clamped using an atraumatic clip for 60 min followed by 3 h of reperfusion. Just upon ending the time of ischemia (removal of clamp artery), animals in MSC-Exo, and H2S-Exo groups received 100 μg exosomes in 100 μl PBS via tail vein. At the end of reperfusion, blood, and liver samples were collected for further serological, molecular, and histological analyses.

RESULTS

Administration of both MSC-Exo and H2S-Exo improved liver function by reducing inflammatory cytokines, cellular apoptosis, liver levels of total oxidant status, and liver aminotransferases. The results showed that protecting effect of MSC exosomes enhanced following NaHS preconditioning of cell culture medium.

CONCLUSION

MSC-Exo and H2S-Exo had hepato-protective effects against injuries induced by ischemia-reperfusion in mice. NaHS preconditioning of mesenchymal stem cells could enhance the therapeutic effects of MSC-derived exosomes.

Transcription Factor YY1 Ameliorates Liver Ischemia-reperfusion Injury Through Modulating the miR-181a-5p/ESR1/ERBB2 Axis

BACKGROUND

Liver ischemia/reperfusion injury (I/RI) is characterized by inflammatory actions. Understanding the mechanistic insights underpinning inflammation is critical to developing treatment strategies. In this study, we illustrated the mechanistic insights of transcription factor Yin-Yang 1 (YY1)-mediated microRNA (miR)-181a-5p/estrogen receptor alpha (ESR1)/epidermal growth factor receptor 2 (ERBB2) axis in liver I/RI.

METHODS

First, we established liver I/RI models in mice and hypoxia-reperfusion (H/R) cell models in mouse hepatocytes (AML12). Subsequently, the expression of YY1, miR-181a-5p, and ESR1 was determined in the 2 models. I/RI mouse models were further injected with lentivirus carrying oe-YY1' and H/R-exposed AML12 cells were subjected to a series of inhibitors, mimics, and shRNAs to validate the mechanisms of YY1 in controlling miR-181a-5p and ESR1 in liver I/RI.

RESULTS

Upregulated expression of miR-181a-5p and downregulated expression of YY1 were identified in the liver tissues of liver I/RI mice and H/R-exposed hepatocytes. Moreover, overexpression of YY1 inhibited the miR-181a-5p expression and thus repressed the H/R-induced hepatocyte apoptosis and inflammation. ESR1 was further validated as a target gene of miR-181a-5p and could be negatively regulated by miR-181a-5p. miR-181a-5p inhibition elevated ESR1 expression, which consequently enhanced the ERBB2 expression and reduced H/R-induced hepatocyte apoptosis and inflammation.

CONCLUSIONS

Overall, these findings highlighted that YY1 repressed the miR-181a-5p expression and stimulated ESR1-mediated activation of ERBB2, thereby ameliorating liver I/RI. This study provides insight into the development of novel targets for liver I/RI.

Ac2-26 attenuates hepatic ischemia-reperfusion injury in mice via regulating IL-22/IL-22R1/STAT3 signaling

Hepatic ischemia-reperfusion injury (HIRI) is one of the major sources of mortality and morbidity associated with hepatic surgery. Ac2-26, a short peptide of Annexin A1 protein, has been proved to have a protective effect against IRI. However, whether it exerts a protective effect on HIRI has not been reported. The HIRI mice model and the oxidative damage model of H₂O₂-induced AML12 cells were established to investigate whether Ac2-26 could alleviate HIRI by regulating the activation of IL-22/IL-22R1/STAT3 signaling. The protective effect of Ac2-26 was measured by various biochemical parameters related to liver function, apoptosis, inflammatory reaction, mitochondrial function and the expressions of IL-22, IL-22R1, p-STAT3^Tyr705. We discovered that Ac2-26 reduced the Suzuki score and cell death rate, and increased the cell viability after HIRI. Moreover, we unraveled that Ac2-26 significantly decreased the number of apoptotic hepatocytes, and the expressions of cleaved-caspase-3 and Bax/Bcl-2 ratio. Furthermore, HIRI increased the contents of malondialdehyde (MDA), NADP⁺/NADPH ratio and reactive oxygen species (ROS), whereas Ac2-26 decreased them significantly. Additionally, Ac2-26 remarkably alleviated mitochondria dysfunction, which was represented by an increase in the adenosine triphosphate (ATP) content and mitochondrial membrane potential, a decrease in mitochondrial DNA (mtDNA) damage. Finally, we revealed that Ac2-26 pretreatment could significantly inhibit the activation of IL-22/IL22R1/STAT3 signaling. In conclusion, this work demonstrated that Ac2-26 ameliorated HIRI by reducing oxidative stress and inhibiting the mitochondrial apoptosis pathway, which might be closely related to the inhibition of the IL-22/IL22R1/STAT3 signaling pathway.

Autophagy Dysregulation in Metabolic Associated Fatty Liver Disease: A New Therapeutic Target

Metabolic associated fatty liver disease (MAFLD) is one of the most common causes of chronic liver disease worldwide. To date, there is no FDA-approved treatment, so there is an urgent need to determine its pathophysiology and underlying molecular mechanisms. Autophagy is a lysosomal degradation pathway that removes damaged organelles and misfolded proteins after cell injury through endoplasmic reticulum stress or starvation, which inhibits apoptosis and promotes cell survival. Recent studies have shown that autophagy plays an important role in removing lipid droplets from hepatocytes. Autophagy has also been reported to inhibit the production of pro-inflammatory cytokines and provide energy for the hepatic stellate cells activation during liver fibrosis. Thyroid hormone, irisin, melatonin, hydrogen sulfide, sulforaphane, DA-1241, vacuole membrane protein 1, nuclear factor erythroid 2-related factor 2, sodium-glucose co-transporter type-2 inhibitors, immunity-related GTPase M, and autophagy-related gene 7 have been reported to ameliorate MAFLD via autophagic induction. Lipid receptor CD36, SARS-CoV-2 Spike protein and leucine aminopeptidase 3 play a negative role in the autophagic function. This review summarizes recent advances in the role of autophagy in MAFLD. Autophagy modulates major pathological changes, including hepatic lipid metabolism, inflammation, and fibrosis, suggesting the potential of modulating autophagy for the treatment of MAFLD.

Mitochondria and Cancer Recurrence after Liver Transplantation—What Is the Benefit of Machine Perfusion?

Tumor recurrence after liver transplantation has been linked to multiple factors, including the recipient’s tumor burden, donor factors, and ischemia-reperfusion injury (IRI). The increasing number of livers accepted from extended criteria donors has forced the transplant community to push the development of dynamic perfusion strategies. The reason behind this progress is the urgent need to reduce the clinical consequences of IRI. Two concepts appear most beneficial and include either the avoidance of ischemia, e.g., the replacement of cold storage by machine perfusion, or secondly, an endischemic organ improvement through perfusion in the recipient center prior to implantation. While several concepts, including normothermic perfusion, were found to reduce recipient transaminase levels and early allograft dysfunction, hypothermic oxygenated perfusion also reduced IRI-associated post-transplant complications and costs. With the impact on mitochondrial injury and subsequent less IRI-inflammation, this endischemic perfusion was also found to reduce the recurrence of hepatocellular carcinoma after liver transplantation. Firstly, this article highlights the contributing factors to tumor recurrence, including the surgical and medical tissue trauma and underlying mechanisms of IRI-associated inflammation. Secondly, it focuses on the role of mitochondria and associated interventions to reduce cancer recurrence. Finally, the role of machine perfusion technology as a delivery tool and as an individual treatment is discussed together with the currently available clinical studies.

Liver Transplant Recipient Characteristics Associated With Worse Post-Transplant Outcomes in Using Elderly Donors

Advanced age of liver donor is a risk factor for graft loss after transplant. We sought to identify recipient characteristics associated with negative post-liver transplant (LT) outcomes in the context of elderly donors. Using 2014–2019 OPTN/UNOS data, LT recipients were classified by donor age: ≥70, 40–69, and <40 years. Recipient risk factors for one-year graft loss were identified and created a risk stratification system and validated it using 2020 OPTN/UNOS data set. At transplant, significant recipient risk factors for one-year graft loss were: previous liver transplant (adjusted hazard ratio [aHR] 4.37, 95%CI 1.98–9.65); mechanical ventilation (aHR 4.28, 95%CI 1.95–9.43); portal thrombus (aHR 1.87, 95%CI 1.26–2.77); serum sodium <125 mEq/L (aHR 2.88, 95%CI 1.34–6.20); and Karnofsky score 10–30% (aHR 2.03, 95%CI 1.13–3.65), 40–60% (aHR 1.65, 95%CI 1.08–2.51). Using those risk factors and multiplying HRs, recipients were divided into low-risk (n = 931) and high-risk (n = 294). Adjusted risk of one-year graft loss in the low-risk recipient group was similar to that of patients with younger donors; results were consistent using validation dataset. Our results show that a system of careful recipient selection can reduce the risks of graft loss associated with older donor age.

Luteolin Pretreatment Attenuates Hepatic Ischemia-Reperfusion Injury in Mice by Inhibiting Inflammation, Autophagy, and Apoptosis via the ERK/PPARα Pathway

Hepatic ischemia-reperfusion (IR) injury is a clinically significant process that frequently occurs in liver transplantation, partial hepatectomy, and hemorrhagic shock. The aim of this study was to explore the effectiveness of luteolin in hepatic IR injury and the underlying mechanism. BALB/c mice were randomly divided into six groups, including normal controls (NC), luteolin (50 mg/kg), sham procedure, IR+25 mg/kg luteolin, and IR+50 mg/kg luteolin group. Serum and tissue samples were collected at 6 and 24 h after reperfusion to assay liver enzymes, inflammatory factors, expression of proteins associated with apoptosis and autophagy, and factors associated with the extracellular signal-regulated kinase/peroxisome proliferator-activated receptor alpha (ERK/PPARα) pathway. Luteolin preconditioning decreased hepatocyte injury caused by ischemia-reperfusion, downregulated inflammatory factors, and inhibited apoptosis and autophagy. Luteolin also inhibited ERK phosphorylation and activated PPARα.

Cordycepin Protects against Hepatic Ischemia/Reperfusion Injury via Inhibiting MAPK/NF-κB Pathway

Hepatic ischemia/reperfusion injury (HIRI) is a common complication of liver surgery requiring hepatic disconnection, such as hepatectomy and liver transplantation. The aim of this study was to investigate the effects of cordycepin on HIRI and to elucidate the underlying mechanisms. Balb/c mice were randomly divided into six groups: a normal control group, sham group, H-cordycepin group, HIRI group, L-cordycepin (25 mg/kg) + HIRI group, and H-cordycepin (50 mg/kg) + HIRI group. Mice were subjected to I/R, and cordycepin was intragastrically administered for seven consecutive days before surgery. Orbital blood and liver specimens were collected at 6 and 24 h after HIRI. Serum levels of ALT and AST were decreased in the cordycepin pretreatment groups. Notably, cordycepin attenuated the inflammatory response and the production of proapoptosis proteins, while increasing expression of antiapoptosis proteins and decreasing expression of autophagy-linked proteins. Furthermore, cordycepin inhibited activation of the MAPK/NF-κB signaling pathway. Collectively, these results indicate that cordycepin pretreatment ameliorated hepatocyte injury caused by HIRI. As compared with the HIRI group, cordycepin pretreatment mitigated the inflammatory response and inhibited apoptosis and autophagy via regulation of the MAPK/NF-κB signaling pathway.

E3 ubiquitin ligase ring finger protein 5 protects against hepatic ischemia reperfusion injury by mediating phosphoglycerate mutase family member 5 ubiquitination

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (HIR) injury, a common clinical complication of liver transplantation and resection, affects patient prognosis. Ring finger protein 5 (RNF5) is an E3 ubiquitin ligase that plays important roles in endoplasmic reticulum stress, unfolded protein reactions, and inflammatory responses; however, its role in HIR is unclear.

APPROACH AND RESULTS

RNF5 expression was significantly down-regulated during HIR in mice and hepatocytes. Subsequently, RNF5 knockdown and overexpression of cell lines were subjected to hypoxia-reoxygenation challenge. Results showed that RNF5 knockdown significantly increased hepatocyte inflammation and apoptosis, whereas RNF5 overexpression had the opposite effect. Furthermore, hepatocyte-specific RNF5 knockout and transgenic mice were established and subjected to HIR, and RNF5 deficiency markedly aggravated liver damage and cell apoptosis and activated hepatic inflammatory responses, whereas hepatic RNF5 transgenic mice had the opposite effect compared with RNF5 knockout mice. Mechanistically, RNF5 interacted with phosphoglycerate mutase family member 5 (PGAM5) and mediated the degradation of PGAM5 through K48-linked ubiquitination, thereby inhibiting the activation of apoptosis-regulating kinase 1 (ASK1) and its downstream c-Jun N-terminal kinase (JNK)/p38. This eventually suppresses the inflammatory response and cell apoptosis in HIR.

CONCLUSIONS

We revealed that RNF5 protected against HIR through its interaction with PGAM5 to inhibit the activation of ASK1 and the downstream JNK/p38 signaling cascade. Our findings indicate that the RNF5-PGAM5 axis may be a promising therapeutic target for HIR.

Aging deteriorated liver Ischemia and reperfusion injury by suppressing Tribble's proteins 1 mediated macrophage polarization

Aggravated liver injury has been reported in aged ischemia/reperfusion-stressed livers; however, the mechanism of aged macrophage inflammatory regulation is not well understood. Here, we found that the adaptor protein TRIB1 plays a critical role in the differentiation of macrophages and the inflammatory response in the liver after ischemia/reperfusion injury. In the present study, we determined that aging promoted macrophage-mediated liver injury and that inflammation was mainly responsible for lower M2 polarization in liver transplantation-exposed humans post I/R. Young and aged mice were subjected to hepatic I/R modeling and showed that aging aggravated liver injury and suppressed macrophage TRIB1 protein expression and anti-inflammatory function in I/R-stressed livers. Restoration of TRIB1 is mediated by lentiviral infection-induced macrophage anti-inflammatory M2 polarization and alleviated hepatic I/R injury. Moreover, TRIB1 overexpression in macrophages facilitates M2 polarization and anti-inflammation by activating MEK1-ERK1/2 signaling under IL-4 stimulation. Taken together, our results demonstrated that aging promoted hepatic I/R injury by suppressing TRIB1-mediated MEK1-induced macrophage M2 polarization and anti-inflammatory function.

Defective mitophagy in aged macrophages promotes mitochondrial DNA cytosolic leakage to activate STING signaling during liver sterile inflammation

Macrophage‐stimulator of interferon genes (STING) signaling mediated sterile inflammation has been implicated in various age‐related diseases. However, whether and how macrophage mitochondrial DNA (mtDNA) regulates STING signaling in aged macrophages remains largely unknown. We found that hypoxia‐reoxygenation (HR) induced STING activation in macrophages by triggering the release of macrophage mtDNA into the cytosol. Aging promoted the cytosolic leakage of macrophage mtDNA and enhanced STING activation, which was abrogated upon mtDNA depletion or cyclic GMP‐AMP Synthase (cGAS) inhibition. Aged macrophages exhibited increased mitochondrial injury with impaired mitophagy. Mechanistically, a decline in the PTEN‐induced kinase 1 (PINK1)/Parkin‐mediated polyubiquitination of mitochondria was observed in aged macrophages. Pink1 overexpression reversed the inhibition of mitochondrial ubiquitination but failed to promote mitolysosome formation in the aged macrophages. Meanwhile, aging impaired lysosomal biogenesis and function in macrophages by modulating the mTOR/transcription factor EB (TFEB) signaling pathway, which could be reversed by Torin‐1 treatment. Consequently, Pink1 overexpression in combination with Torin‐1 treatment restored mitophagic flux and inhibited mtDNA/cGAS/STING activation in aged macrophages. Moreover, besides HR‐induced metabolic stress, other types of oxidative and hepatotoxic stresses inhibited mitophagy and promoted the cytosolic release of mtDNA to activate STING signaling in aged macrophages. STING deficiency protected aged mice against diverse types of sterile inflammatory liver injuries. Our findings suggest that aging impairs mitophagic flux to facilitate the leakage of macrophage mtDNA into the cytosol and promotes STING activation, and thereby provides a novel potential therapeutic target for sterile inflammatory liver injury in aged patients.

Long non-coding RNA MALAT1 aggravated liver ischemia-reperfusion injury via targeting miR-150-5p/AZIN1

Long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays a crucial role in the process of renal ischemia-reperfusion (IR) injury and myocardial IR injury. However, its mechanism in liver IR injury is not clear. IR and hypoxia/reoxygenation (H/R) model were built on C57BL/6 mice. Blood samples were obtained from the inferior vena cava of the model mice. MALAT1 expression was detected in IR model and H/R model. Supported by experimental results, the impacts of MALAT1 on viability, apoptosis, and inflammation of H/R model cells were detected. The correlation between MALAT1 and downstream genes was analyzed by mechanism assays. MALAT1 was detected to be upregulated in IR model and H/R model. MALAT1 knockdown had inhibitory effects on apoptosis and inflammatory reaction while promoting liver cell viability in H/R condition. Meanwhile, MALAT1 targeted miR-150-5p to regulate antizyme inhibitor 1 (AZIN1) in liver cells. Finally, MALAT1 regulated viability, apoptosis, and inflammatory reaction of liver cells by targeting miR-150-5p and AZIN1. To conclude, MALAT1 targeted miR-150-5p/AZIN1 to accelerate liver IR injury, suggesting that MALAT1 might be a novel target for liver IR injury.

The role of Resolvin D1 in liver diseases

The liver is a parenchymatous organ closely related to immunity, detoxification and metabolism of the three major nutrients. The inflammatory response is a protective mechanism of the body to eliminate harmful stimuli. However, continuous inflammatory stimulation leads to occurrence of many liver diseases and brings great social burden. Resolvin D1, a member of the specialized pro-resolving lipid mediators family, exerts anti-inflammatory, anti-oxidant stress, anti-fibrosis, anti-apoptotic, and anti-tumor effects by binding to ALX/FPR2 or GPR32. RvD1 plays an important role and has great therapeutic potential in liver diseases, which has been validated in multiple models of preclinical disease. This review will provide a detailed summary of the role of RvD1 in different liver diseases, including acute liver injury, liver ischemia/reperfusion injury, non-alcoholic fatty liver disease, liver fibrosis, and liver cancer, so as to help people have a more comprehensive understanding of RvD1 and promote its further research.

Regulator of G-protein signaling 14 protects the liver from ischemia-reperfusion injury by suppressing TGF-β-activated kinase 1 activation

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion injury (IRI) is a common complication of hepatectomy and liver transplantation. However, the mechanisms underlying hepatic IRI have not been fully elucidated. Regulator of G-protein signaling 14 (RGS14) is a multifunctional scaffolding protein that integrates the G-protein and mitogen-activated protein kinase (MAPK) signaling pathways. However, the role of RGS14 in hepatic IRI remains unclear.

APPROACH AND RESULTS

We found that RGS14 expression increased in mice subjected to hepatic ischemia-reperfusion (IR) surgery and during hypoxia reoxygenation in hepatocytes. We constructed global RGS14 knockout (RGS14-KO) and hepatocyte-specific RGS14 transgenic (RGS14-TG) mice to establish 70% hepatic IRI models. Histological hematoxylin and eosin staining, levels of alanine aminotransferase and aspartate aminotransferase, expression of inflammatory factors, and apoptosis were used to assess liver damage and function in these models. We found that RGS14 deficiency significantly aggravated IR-induced liver injury and activated hepatic inflammatory responses and apoptosis in vivo and in vitro. Conversely, RGS14 overexpression exerted the opposite effect of the RGS14-deficient models. Phosphorylation of TGF-β-activated kinase 1 (TAK1) and its downstream effectors c-Jun N-terminal kinase (JNK) and p38 increased in the liver tissues of RGS14-KO mice but was repressed in those of RGS14-TG mice. Furthermore, inhibition of TAK1 phosphorylation rescued the effect of RGS14 deficiency on JNK and p38 activation, thus blocking the inflammatory responses and apoptosis.

CONCLUSIONS

RGS14 plays a protective role in hepatic IR by inhibiting activation of the TAK1-JNK/p38 signaling pathway. This may be a potential therapeutic strategy for reducing incidences of hepatic IRI in the future.

STING Induces Liver Ischemia-Reperfusion Injury by Promoting Calcium-Dependent Caspase 1-GSDMD Processing in Macrophages

Objectives

Although a recent study reported that stimulator of interferon genes (STING) in macrophages has an important regulatory effect on liver ischemia-reperfusion injury (IRI), the underlying mechanism of STING-dependent innate immune activation in liver macrophages (Kupffer cells, KCs) remains unclear. Here, we investigated the effect of STING on liver macrophage pyroptosis and the associated regulatory mechanism of liver IRI.

Methods

Clodronate liposomes were used to block liver macrophages. AAV-STING-RNAi-F4/80-EGFP, an adenoassociated virus (AAV), was transfected into the portal vein of mice in vivo, and the liver IRI model was established 14 days later. In vitro, liver macrophages were treated with STING-specific siRNA, and a hypoxia-reoxygenation (H/R) model was established. The level of STING was detected via Western blotting (WB), RT-PCR, and immunostaining. Liver tissue and blood samples were collected. Pathological changes in liver tissue were detected by hematoxylin and eosin (H&E) staining. Macrophage pyroptosis was detected by WB, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and enzyme-linked immunosorbent assay (ELISA). The calcium concentration was measured by immunofluorescence and analyzed with a fluorescence microplate reader.

Results

The expression of STING increased with liver IRI but decreased significantly after the clodronate liposome blockade of liver macrophages. After knockdown of STING, the activation of caspase 1-GSDMD in macrophages and liver IRI was alleviated. More interestingly, hypoxia/reoxygenation (H/R) increased the calcium concentration in liver macrophages, but the calcium concentration was decreased after STING knockdown. Furthermore, after the inhibition of calcium in H/R-induced liver macrophages by BAPTA-AM, pyroptosis was significantly reduced, but the expression of STING was not significantlydecreased.

Conclusions

Knockdown of STING reduces calcium-dependent macrophage caspase 1-GSDMD-mediated liver IRI, representing a potential therapeutic approach in the clinic.

Noncoding RNA Roles in Pharmacogenomic Responses to Aspirin: New Molecular Mechanisms for an Old Drug

Aspirin, as one of the most frequently prescribed drugs, can have therapeutic effects on different conditions such as cardiovascular and metabolic disorders and malignancies. The effects of this common cardiovascular drug are exerted through different molecular and cellular pathways. Altered noncoding RNA (ncRNA) expression profiles during aspirin treatments indicate a close relationship between these regulatory molecules and aspirin effects through regulating gene expressions. A better understanding of the molecular networks contributing to aspirin efficacy would help optimize efficient therapies for this very popular drug. This review is aimed at discussing and highlighting the identified interactions between aspirin and ncRNAs and their targeting pathways and better understanding pharmacogenetic responses to aspirin.

Autophagy deficiency promotes M1 macrophage polarization to exacerbate acute liver injury via ATG5 repression during aging

Aging disrupts the maintenance of liver homeostasis, which impairs hepatocyte regeneration and aggravates acute liver injury (ALI), ultimately leading to the development of acute liver failure (ALF), a systemic inflammatory response, and even death. Macrophages influence the progression and outcome of ALI through the innate immune system. However, it is still unclear how macrophages regulate ALI during aging. The variation in macrophage autophagy with aging and the influence on macrophage polarization and cytokine release were assessed in BMDMs in vitro. Then, after BMDMs subjected to several treatments were intravenously or intraperitoneally injected into mice, thioacetamide (TAA)-induced ALI (TAA-ALI) was established, and its effects on inflammation, injury, and mortality were assessed. We found that aging aggravated the liver injury, along with increases in the levels of proinflammatory mediators, presenting a senescence-associated secretory phenotype (SASP), which promoted macrophage polarization to the M1 phenotype. In addition, autophagy levels decreased significantly in aged mice, which was ascribed to ATG5 repression during aging. Notably, enhancing autophagy levels in aged BMDMs restored macrophage polarization to that observed under young conditions. Finally, autophagy restoration in aged BMDMs enhanced the protective effect against TAA-ALI, similar to M2 macrophages induced by IL-4. Overall, we demonstrated that the influence of aging on macrophage polarization is an important aggravating factor in TAA-ALI, and the autophagy in macrophages is associated with the aging phenotype.

Autophagic activation of IRF-1 aggravates hepatic ischemia-reperfusion injury via JNK signaling

Increasing evidence has accrued indicating that autophagy is associated with hepatic ischemia-reperfusion injury (IRI). This report demonstrates that interferon regulatory factor-1 (IRF-1) was upregulated in response to hepatic IRI and was associated with autophagic activation. As a result of these processes, there is an aggravation of liver damage, effects that can be offset by IRF-1 depletion. In addition, these effects of IRF-1 are associated with JNK pathway activation followed by increases in Beclin1 protein levels. This JNK-induced autophagic cell death then leads to cell failure, and plays an important role in liver function damage. We conclude that IRF-1 activates autophagy through JNK-mediated autophagy. Accordingly, these findings indicating that the IRF-1/JNK pathway activates autophagy to exacerbate liver IRI in this mouse model may provide new insights into novel protective therapies for hepatic IRI.

Thrombomodulin-mediated Inhibition of Neutrophil Extracellular Trap Formation Alleviates Hepatic Ischemia/Reperfusion Injury by Blocking TLR4 in Rats Subjected to Liver Transplantation

BACKGROUND

Hepatic ischemia/reperfusion injury (IRI) is an unavoidable outcome of liver transplantation, during which neutrophil extracellular traps (NETs) may play a critical role in the IRI-induced immune response to inflammation. The purpose of this study was to identify the function of recombinant human thrombomodulin (rTM) in the remission of hepatic IRI after liver transplantation and elucidate the specific mechanism.

METHODS

NET formation was detected in the serum of liver transplantation patients and rats following liver transplantation. Hematoxylin-eosin (HE) staining, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining, immunohistochemistry and immunofluorescence were used to assess the effect of rTM on NET formation in vitro and in vivo.

RESULTS

We found that rTM markedly inhibited neutrophil formation in NETs, reduced apoptosis in hepatocytes, alleviated rat hepatic IRI and improved liver function. In vitro, rTM inhibited neutrophil formation in NETs, and lipopolysaccharide (LPS) (a Toll-like receptor (TLR)-4 agonist) reversed the inhibitory effect of rTM on NET formation. rTM blocked TLR-4 and the downstream extracellular signal-regulated kinase (ERK)/c-Jun NH2 terminal kinase (JNK) and nicotinamide adenine dinucleotide phosphate (NADPH)/ROS/peptidylarginine deiminase 4 (PAD4) signaling pathways to protect against hepatic IRI and inhibit NET formation. In addition, we demonstrated that combined treatment with rTM and an NADPH oxidative inhibitor had a better effect than either treatment alone.

CONCLUSIONS

NETs are a potential therapeutic target in hepatic IRI, and rTM could be used to prevent IR-induced hepatic injury. In addition, cotargeting NETosis-related signaling pathways might be a novel therapeutic strategy for hepatic IRI treatment.

Methods of Attenuating Ischemia-Reperfusion Injury in Liver Transplantation for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent indications for liver transplantation. However, the transplantation is ultimately associated with the occurrence of ischemia-reperfusion injury (IRI). It affects not only the function of the graft but also significantly worsens the oncological results. Various methods have been used so far to manage IRI. These include the non-invasive approach (pharmacotherapy) and more advanced options encompassing various types of liver conditioning and machine perfusion. Strategies aimed at shortening ischemic times and better organ allocation pathways are still under development as well. This article presents the mechanisms responsible for IRI, its impact on treatment outcomes, and strategies to mitigate it. An extensive review of the relevant literature using MEDLINE (PubMed) and Scopus databases until September 2020 was conducted. Only full-text articles written in English were included. The following search terms were used: “ischemia reperfusion injury”, “liver transplantation”, “hepatocellular carcinoma”, “preconditioning”, “machine perfusion”.

Downregulation of miR-497-5p prevents liver ischemia-reperfusion injury in association with MED1/TIMP-2 axis and the NF-κB pathway

Liver ischemia-reperfusion (I/R) injury is a common clinical pathological phenomenon, which is accompanied by the occurrence in liver transplantation. However, the underlying mechanism is not yet fully understood. MicroRNAs (miRNAs) play an important role in liver I/R injury. Therefore, the study of miRNAs function will contribute a new biological marker diagnosis of liver I/R injury. This study aims to evaluate effects of miR-497-5p in liver I/R injury in mice. The related regulatory factors of miR-497-5p in liver I/R injury were predicted by bioinformatics analysis. Vascular occlusion was performed to establish the liver I/R injury animal models. Hypoxia/reoxygenation (H/R) was performed to establish the in vitro models. Hematoxylin-eosin (HE) staining was conducted to assess liver injury. The inflammatory factors were evaluated by enzyme-linked immunosorbent assay (ELISA). Flow cytometry was adopted to assess the cell apoptosis. The expression of miR-497b-5p was increased in liver I/R injury. Knockdown of miR-497b-5p inhibited the production of inflammatory factors and cell apoptosis. Overexpression of mediator complex subunit 1 (MED1) and tissue inhibitor of metalloproteinase 2 (TIMP2) inhibited cell apoptosis to alleviate liver I/R injury. miR-497b-5p could activate the nuclear factor kappa-B (NF-κB) pathway by inhibiting the MED1/TIMP-2 axis to promote liver I/R injury. This study may provide a new strategy for the treatment of liver I/R injury.

Notoginsenoside R1 protects hypoxia-reoxygenation deprivation-induced injury by upregulation of miR-132 in H9c2 cells

BACKGROUND

Myocardial ischemia/reperfusion injury (IRI) is a common perioperative complication of heart and great vessels surgery, aggravating the original myocardial damage and seriously affecting the postoperative recovery of cardiac function. The aim of this study was to reveal the functional effects and potential mechanisms of notoginsenoside R1 (NG-R1) in myocardial cells injured by hypoxia-reoxygenation (H/R).

METHODS

The rat cardiomyocyte line H9c2 was subjected to H/R with or without NG-R1 treatment. The levels of miR-132 and HBEGF in the cell were altered by microRNA or short-hairpin RNA transfection. Cell viability, apoptosis, lactate dehydrogenase (LDH) and malondialdehyde (MDA) were monitored. Dual luciferin was used to detect the relationship between miR-132 and HBEGF.

RESULTS

NG-R1 (20 μM) had no impact on H9c2 cells, but cell viability was significantly reduced at 80 μM. NG-R1 (20 μM) protected H9c2 cells against H/R-induced cell damage, accompanied by increased cell viability, reduced cell apoptosis, and downregulation of LDH and MDA. Furthermore, the level of miR-132 was decreased in response to H/R exposure but then increased after NG-R1 treatment. When miR-132 was overexpressed, H/R-induced cell damage could be recovered. Downregulation of miR-132 limited the protective effect of NG-R1 on H/R damage. We also found that HBEGF was a direct target of miR-132. The expression of HBEGF was increased upon H/R damage, and this increase was reversed after NG-R1 treatment.

CONCLUSIONS

This study demonstrated that NG-R1 markedly protected H9c2 cells against H/R-induced damage via upregulation of miR-132 and downregulation of its target protein HBEGF.

Paeonol Pretreatment Attenuates Anoxia-Reoxygenation Induced Injury in Cardiac Myocytes via a BRCA1 Dependent Pathway

Breast cancer type 1 sensitive protein (BRCA1) is a well-known tumor suppressor and its role in oxidative stress has been confirmed. The purpose of this study is to evaluate whether paeonol has a protective effect on myocardial hypoxia-reoxygenation (A/R) injury, and to explore H9C2 cells through a mechanism-dependent pathway mediated by BRCA1. H9C2 cells were pretreated with paeonol (10 µM) for 18 h before hypoxia was induced to establish a cell model of myocardial ischemia/reperfusion (I/R) injury. Use commercial kits to detect antioxidant indicators, including relative oxygen content (ROS) levels, total antioxidant capacity (T-AOC), superoxide dismutase (SOD), lactate dehydrogenase (LDH) activity, and creatine kinase (CK-MB) and nuclear factor-kappaB (NF-κB) activity. The cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction method. Real-time fluorescent quantitative PCR was used to detect BRCA1 mRNA and protein levels. The expression levels of BRCA1, NLRP3 and ACS were determined by Western blotting. In addition, the release of interleukin (IL)-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) was also evaluated by an enzyme-linked immunosorbent assay (ELISA) kit. The results showed that paeonol (10 µM) can significantly improve the hypoxic A/R damage of H9C2 cells, and the BRCA1 expression of H9C2 cells pretreated with paeonol was significantly increased before A/R damage was induced. BRCA1 is widely known in breast and ovarian cancer. Our data proves that the down-regulation of BRCA1 participates in the decrease of cell viability and the decrease of CK-MB and LDH activities, and protects cells by inhibiting the production of ROS and the activation of Nod-like receptor protein 3 (NLRP3) inflammasomes and NF-κB. In conclusion, paeonol significantly improved the A/R damage of H9C2 cells induced by hypoxia through the BRCA1/ROS-regulated NLRP3 inflammasome/IL-1β and NF-κB/TNF-α/IL-6 pathways. It may be a potential drug against myocardial I/R injury.

Histone deacetylase‑2: A potential regulator and therapeutic target in liver disease (Review)

Histone acetyltransferases are responsible for histone acetylation, while histone deacetylases (HDACs) counteract histone acetylation. An unbalanced dynamic between histone acetylation and deacetylation may lead to aberrant chromatin landscape and chromosomal function. HDAC2, a member of class I HDAC family, serves a crucial role in the modulation of cell signaling, immune response and gene expression. HDAC2 has emerged as a promising therapeutic target for liver disease by regulating gene transcription, chromatin remodeling, signal transduction and nuclear reprogramming, thus receiving attention from researchers and clinicians. The present review introduces biological information of HDAC2 and its physiological and biochemical functions. Secondly, the functional roles of HDAC2 in liver disease are discussed in terms of hepatocyte apoptosis and proliferation, liver regeneration, hepatocellular carcinoma, liver fibrosis and non-alcoholic steatohepatitis. Moreover, abnormal expression of HDAC2 may be involved in the pathogenesis of liver disease, and its expression levels and pharmacological activity may represent potential biomarkers of liver disease. Finally, research on selective HDAC2 inhibitors and non-coding RNAs relevant to HDAC2 expression in liver disease is also reviewed. The aim of the present review was to improve understanding of the multifunctional role and potential regulatory mechanism of HDAC2 in liver disease.

Impact of donor age on liver transplant outcomes in patients with hepatocellular carcinoma: analysis of the SRTR database

Background

Donor age is an important predictor for liver transplant recipients. Studies have not fully explored its impact on transplant outcomes in hepatocellular carcinoma (HCC) patients as well as its involvement in tumor recurrence.

Methods

HCC patients who received liver transplants during 2010–2017 from the Scientific Registry of Transplant Recipients database were included. The recipients were divided into four groups based on donor age: I (≤ 34 years), II (35–49 years), III (50–64 years), and IV (≥ 65 years). Transplant outcomes, including the overall survival (OS), tumor recurrence, and risks, were evaluated.

Results

A total of 13,276 HCC recipients were included in this study. Statistical significant differences were observed in OS among the four groups. The best 5-year survival was 76.0% in group I, followed by 73.5% in group II, 72.8% in group III, and 69.2% in group IV (P < 0.001). However, the liver-specific survival did not differ among these groups (P = 0.260). Donor age was found to be the independent predictor of OS after adjusting for other variables (P < 0.001, ref. group I; 1.087 (0.979–1.208) for group II, P = 0.119; 1.124 (1.015–1.246) for group III, P = 0.025; 1.395 (1.215–1.602) for group IV, P < 0.001). In subgroup analysis, OS was significantly different in recipients with hepatitis C virus (HCV), but there was no significant difference for recipients with hepatitis B virus (HBV), alcoholic liver diseases and nonalcoholic steatohepatitis (NASH). The post-transplant cumulative tumor recurrence rates were similar among the four groups (P = 0.382).

Conclusions

Older donor age was associated with decreased OS but not liver-specific survival as well as post-transplant tumor recurrence in HCC recipients. Donor age also had different effects in patients with different underlying liver diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-01786-6.

Resveratrol Alleviates Vascular Endothelial Damage Caused by Lower-Extremity Ischemia Reperfusion (I/R) through Regulating Keap1/Nrf2 Signaling-Mediated Oxidative Stress

The present study aims to investigate the protective effects of Resveratrol (RSV) against vascular endothelial damage caused by lower-extremity I/R and the underlying preliminary mechanism. The in vitro hypoxia reoxygenation (HR) model was established on HUVECs. Lower-extremity I/R model was established on rats followed by being treated with RSV and the pathological state of artery was evaluated by HE and EVG staining, while the apoptotic state of artery was detected by TUNEL assay. The cell viability was detected by MTT assay and the apoptotic state of cells was determined by Hoechst test and flow cytometry assay. DCFH-DA staining was used to measure the level of ROS and the production of MDA and SOD was measured by commercial kits. The expression level of Nrf2, Keap1, HO-1, Bcl-2, Bax, and Caspase-3 in cells was determined by Western blot. Nrf2 was knocked down by siRNA technology. Overall, our data indicated that increased cell viability, declined apoptotic rate, and alleviated oxidative stress were observed in RSV treated HR HUVECs, which were significantly reversed by knocking down Nrf2. Animal experiment revealed that the pathological and apoptotic state of femoral artery were dramatically ameliorated by the treatment of RSV, accompanied by the alleviated oxidative stress, which were abolished by the co-administration of ML385, an inhibitor of Nrf2. Taken together, our data revealed that RSV might alleviate vascular endothelial injury induced by lower-extremity I/R injury through regulating Keap1/Nrf2 signaling-mediated oxidative stress.

Pemafibrate Pretreatment Attenuates Apoptosis and Autophagy during Hepatic Ischemia-Reperfusion Injury by Modulating JAK2/STAT3β/PPARα Pathway

Hepatic ischemia-reperfusion injury (HIRI) is a common phenomenon in liver transplantation and liver surgery. This article is aimed at clarifying the role of pemafibrate in HIRI through JAK2/STAT3β/PPARα. In the experiment, we divided Balb/c into seven groups, namely, normal control (NC), Sham, PEM (1.0 mg/kg), IRI, IRI + PEM (0.1 mg/kg), IRI + PEM (0.5 mg/kg), and IRI + PEM (1.0 mg/kg). We used biochemical assay, histopathological evaluation, immunohistochemistry, RT-PCR and qRT-PCR, ELISA analysis, and other methods to determine the level of serum AST, ALT, IL-1β, and TNF-α in the liver at three time points (2 h, 8 h, and 24 h) after reperfusion of apoptosis factor, autophagy factor, and the JAK2/STAT3/PPARα content in tissues. Our experiment results showed that the pemafibrate can effectively reduce the level of hepatic IR injury. In addition, pemafibrate has anti-inflammatory, antiapoptotic, and antiautophagy effects, which are mediated by the JAK2/STAT3β/PPARα pathway.

microRNA-145 Inhibition Upregulates SIRT1 and Attenuates Autophagy in a Mouse Model of Lung Ischemia/Reperfusion Injury via NF-κB-dependent Beclin 1

BACKGROUND

MicroRNA-145 (miR-145) has been shown to play a critical role in ischemia/reperfusion (I/R) injury; however, the expression and function of miR-145 in lung I/R injury have not been reported yet. This study aimed to elucidate the potential effects of miR-145 in lung I/R injury.

METHODS

Lung I/R mice models and hypoxia/reoxygenation (H/R) pulmonary microvascular endothelial cell models were established. The expression of miR-145 and sirtuin 1 (SIRT1) was measured with reverse transcription-quantitative polymerase chain reaction and Western blot analysis in mouse lung tissue and cells. Artificial modulation of miR-145 and SIRT1 (downregulation) was done in I/R mice and H/R cells. Additionally, Pao2/FiO2 ratio, wet weight-to-dry weight ratio, and cell apoptosis in mouse lung tissues were determined by blood gas analyzer, electronic balance, and deoxyuridine triphosphate-biotin nick end-labeling assay, respectively. Autophagy marker Beclin 1 and LC3 expression, NF-κB acetylation levels, and autophagy bodies were detected in cell H/R and mouse I/R models by Western blot analysis. pulmonary microvascular endothelial cell apoptosis was detected with flow cytometry.

RESULTS

miR-145 was abundantly expressed in the lung tissue of mice and PMVECs following I/R injury. In addition, miR-145 directly targeted SIRT1, which led to significantly decreased Pao2/FiO2 ratio and increased wet weight-to-dry weight ratio, elevated acetylation levels and transcriptional activity of NF-κB, upregulated expressions of tumor necrosis factor-α, interleukins-6, and Beclin 1, autophagy bodies, cell apoptosis, as well as LC3-II/LC3I ratio.

CONCLUSIONS

In summary, miR-145 enhances autophagy and aggravates lung I/R injury by promoting NF-κB transcriptional activity via SIRT1 expression.

BET Protein Inhibition Prolongs Cardiac Transplant Survival via Enhanced Myocardial Autophagy

BACKGROUND

Graft rejection continues to be a major barrier to long-term engraftment after transplantation. Autophagy plays an important role in cardiac injury pathogenesis. The bromodomain and extraterminal protein inhibitor (S)-tert-butyl2-(4-(4-chlorophenyl)-2,3,9-trimethyl-6H-thieno[3,2-f][1,2,4]triazolo[4,3-a][1,4]diazepin-6-yl)acetate (JQ1) inhibits inflammatory responses. However, the beneficial effect of JQ1 on transplant and the potential role of autophagy in the protective effect of graft survival are yet to be investigated.

METHODS

Syngeneic or allogeneic heterotopic heart transplantation was performed using C57BL/6 or BALB/c donors for C57BL/6 recipients through different treatments. Some mice were used to observe the survival of the grafts. The other mice were euthanized on the third, fifth, and seventh days after surgery. The graft samples were taken for cytokines and autophagy pathway analyses.

RESULTS

Our study revealed that JQ1 treatment prolonged cardiac allograft survival. JQ1 increased the expression levels of liver kinase beta 1, autophagy-specific gene 5, and microtubule-associated protein light chain3-II (LC3-II) and potentiated the phosphorylation of AMP-activated protein kinase, unc-51-like kinase 1 (ULK1), and autophagy-specific gene 14 in allografts. A conditional autophagy-specific gene 5 deletion donor was utilized to abrogate the effect induced by JQ1. The combined use of JQ1 with bafilomycin A1 partially reversed the effect of JQ1, suggesting that autophagy is involved in the signaling pathway in graft survival. JQ1 downregulated the expression of inflammatory cytokines, such as interleukin-6, interleukin-1β, tumor necrosis factor-α, and interferon-γ, which was abrogated when autophagy was inhibited.

CONCLUSIONS

JQ1 prolonged cardiac allograft survival by potentiating myocardial autophagy through the liver kinase beta 1-AMP-activated protein kinase-ULK1 signaling pathway and inhibiting the subsequent release of inflammatory cytokines. This result might provide novel insights for extending transplant survival.

Effects of remote ischemic preconditioning on liver injury following hepatectomy: a systematic review and meta-analysis of randomized control trials

The protective effect of remote ischemic preconditioning (RIPC) against liver ischemia-reperfusion injury caused by hepatectomy remains controversial. We conducted this meta-analysis to evaluate the effectiveness and safety of RIPC strategies. PubMed, SinoMed, Embase, Cochrane Library, Medline, and Web of Science databases were searched for randomized controlled trials (RCT) that assessed the effectiveness and safety of RIPC strategies. The primary outcomes were operation time, index of liver function on postoperative day (POD) 1, postoperative complications, and postoperative hospital stay. The pooled odds ratios and weighted mean differences at 95% confidence interval (95% CI) were estimated using a fixed-effects or random-effects model. A total of 459 patients were included in seven RCTs. The alanine aminotransferase (ALT) and alanine aminotransferase (AST) values on POD1 were significantly different between the RIPC group and the N-RIPC group (P = 0.009 and P = 0.02, respectively). However, the heterogeneity was significant (I² = 84% and I² = 86%), and the results of a sensitivity analysis were unstable. There was no significant difference in the total bilirubin levels (P = 0.25) between the two groups on POD1. Subgroup analysis revealed no significant difference in the AST and ALT levels on POD1 between the RIIPC group and the N-RIPC group, regardless of whether the vascular control technique was used (all P > 0.05). Based on current evidence, RIPC does not alleviate liver injury caused by IRI after hepatectomy.

Aucubin Attenuates Liver Ischemia-Reperfusion Injury by Inhibiting the HMGB1/TLR-4/NF-κB Signaling Pathway, Oxidative Stress, and Apoptosis

Liver ischemia-reperfusion injury (IRI) is a common clinical event with high morbidity in patients undergoing complex liver surgery or having abdominal trauma. Inflammatory and oxidative stress responses are the main contributing factors in liver IRI. The iridoid glucoside aucubin (AU) has good anti-inflammatory and antioxidative effects; however, there are no relevant reports on the protective effect of glucosides on hepatic IRI. The purpose of this study was to determine whether AU pretreatment could prevent liver IRI and to explore the mechanism. Sprague–Dawley rats were randomly divided into five groups. The sham operation and IRI control groups were given intraperitoneal injections of normal saline, while the AU low-dose (AU-L) group, AU medium-dose (AU-M) group, and AU high-dose (AU-H) group were given intraperitoneal injections of AU at doses of 1, 5, and 10 mg/kg/day, respectively. After 10 d, liver IRI (70% liver ischemia for 1 h, reperfusion for 6 h) was surgically established in all groups except the sham group. Our results confirmed that liver injury was significantly aggravated after hepatic ischemia-reperfusion. AU alleviated the increase of transaminase and pathological changes induced by ischemia-reperfusion and improved liver damage. AU could also ameliorate the inflammatory and oxidative stress responses induced by ischemia-reperfusion and reduced expression of high mobility group protein (HMG)B1, receptor for advanced glycation end-products (RAGE), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and reactive oxygen species (ROS). Moreover, AU reduced ischemia-reperfusion-induced mitochondrial dysfunction and cells apoptosis, increased peroxisome proliferator-activated receptor γ coactivator (PGC)-1α and uncoupling (UCP)2 protein expression, and reduced caspase-3, cleaved caspase-3, and Cytochrome P450 proteins (CYP) expression. To determine expression levels of the Toll-like receptor (TLR)-4/nuclear factor-κB (NF-κB) pathway-related proteins in vitro and in vivo, we also measured TLR-4, myeloid differentiation factor88 (MyD88), NF-κB P65, p-P65, I-kappa-B-alpha (IκB-α), and p-IκB-α levels. The results showed that AU effectively inhibited activation of the TLR-4/NF-κB signaling pathway. In conclusion, we showed for the first time a hepatoprotective effect for AU in liver IRI, which acted by inhibiting the HMGB1/TLR-4/NF-κB signaling pathway, oxidative stress, and apoptosis. Pretreatment with AU may be a promising strategy for preventing liver IRI.

Advances in the pathogenesis and prevention of contrast-induced nephropathy

With the increasing application of medical imaging contrast materials, contrast-induced nephropathy has become one of the leading causes of iatrogenic renal insufficiency. The underlying mechanism is associated with renal medullary hypoxia, direct toxicity of contrast agents, oxidative stress, apoptosis, immune/inflammation and epigenetic regulation in contrast-induced nephropathy. Up to date, there is no effective therapy for contrast-induced nephropathy, and thus risk predication and effective preventive strategies are keys to reduce the occurrence of contrast-induced nephropathy. It was found that the proper use of contrast medium, personalized hydration, and high-dose statins may reduce the occurrence of contrast-induced nephropathy, while antioxidants have not shown significant therapeutic benefits. Additionally, the role of remote ischemia preconditioning and vasodilators in the prevention of contrast-induced nephropathy needs further study. This review aims to discuss the incidence, pathogenesis, risk prediction, and preventive strategies for contrast-induced nephropathy.

Aging aggravated liver ischemia and reperfusion injury by promoting STING-mediated NLRP3 activation in macrophages

Although aggravated liver injury has been reported in aged livers post‐ischemia and reperfusion (IR), the underlying mechanism of innate immune activation of aged macrophages is not well understood. Here, we investigated whether and how Stimulator of interferon genes (STING) signaling regulated macrophage proinflammatory activation and liver IR injury. Mice were subjected to hepatic IR in vivo. Macrophages isolated from IR‐stressed livers and bone marrow‐derived macrophages (BMDMs) from young and aged mice were used for in vitro studies. Enhanced nucleotide‐binding domain and leucine‐rich repeat containing protein 3 (NLRP3) activation was found in both livers and macrophages of aged mice post‐IR. NLRP3 knockdown in macrophages inhibited intrahepatic inflammation and liver injury in both young and aged mice. Interestingly, enhanced activation of the STING/ TANK‐binding kinase 1 (TBK1) signaling pathway was observed in aged macrophages post‐IR and mitochondria DNA (mtDNA) stimulation. STING suppression blocked over‐activation of NLRP3 signaling and excessive secretion of proinflammatory cytokines/chemokines in the mtDNA‐stimulated BMDMs from aged mice. More importantly, STING knockdown in macrophages abrogated the detrimental role of aging in aggravating liver IR injury and intrahepatic inflammation. Finally, peripheral blood from the recipients undergoing liver transplantation was collected and analyzed. The results showed that the elderly recipients had much higher levels of TNF‐α, IL‐6, IL‐1β, and IL‐18 post‐transplantation, indicating increased NLRP3 activation in lR‐stressed livers of elderly recipients. In summary, our study demonstrated that the STING‐NLRP3 axis was critical for the proinflammatory response of aged macrophages and would be a novel therapeutic target to reduce IR injury in elderly patients.

Sirtuin-1 expression and activity is diminished in aged liver grafts

The cellular mechanisms underlying impaired function of aged liver grafts have not been fully elucidated, but mitochondrial dysfunction appears to be contributory. Sirtuin1 has been identified as a key mediator of mitochondrial recovery following ischemia-reperfusion injury. The purpose of this study was to determine whether differences exist in sirtuin-1 expression/activity in old vs. young liver grafts and to determine correlations with mitochondrial function, graft metabolic function, and graft injury. Old and young rat liver grafts (N = 7 per group) were exposed to 12 h of static cold storage (SCS), followed by a 2 h period of graft reperfusion ex vivo. Sirtuin1 expression and activity, mitochondrial function, graft metabolic function, and graft injury were compared. Sirtuin1 expression is upregulated in young, but not old, liver grafts in response to cold storage and reperfusion. This is associated with diminished tissue ATP, antioxidant defense, and graft metabolic function in old liver grafts. There was no evidence of increased inflammation or histologic injury in old grafts. Sirtuin1 expression is diminished in old liver grafts and correlates with mitochondrial and metabolic function. The sirtuin pathway may represent a target for intervention to enhance the function of aged liver grafts.