Molecular biology of liver ischemia/reperfusion injury: established mechanisms and recent advancements

Role of hydrogen sulfide in health and disease

In the past, hydrogen sulfide (H2S) was recognized as a toxic and dangerous gas; in recent years, with increased research, we have discovered that H2S can act as an endogenous regulatory transmitter. In mammals, H2S-catalyzing enzymes, such as cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase, are differentially expressed in a variety of tissues and affect a variety of biological functions, such as transcriptional and posttranslational modification of genes, activation of signaling pathways in the cell, and metabolic processes in tissues, by producing H2S. Various preclinical studies have shown that H2S affects physiological and pathological processes in the body. However, a detailed systematic summary of these roles in health and disease is lacking. Therefore, this review provides a thorough overview of the physiological roles of H2S in different systems and the diseases associated with disorders of H2S metabolism, such as ischemia-reperfusion injury, hypertension, neurodegenerative diseases, inflammatory bowel disease, and cancer. Meanwhile, this paper also introduces H2S donors and novel release modes, as well as the latest preclinical experimental results, aiming to provide researchers with new ideas to discover new diagnostic targets and therapeutic options.

Diagnosis and Molecular Characterization of Potential RNA Binding Protein Involved in the Pathogenesis of Liver Ischemia Reperfusion Injury

Background

Liver ischemia-reperfusion is one of the common complications after liver surgery. Uncontrolled liver ischemia-reperfusion will lead to many serious consequences such as surgical failure. It is an urgent clinical problem to search for diagnostic markers and explore its potential pathogenesis.

Methods

In this study, we focus on 1411 candidate RNA binding protein. Through several GEO (Gene Expression Omnibus) online datasets, we construct a diagnostic model and perform interactive validation. We evaluate the efficacy of the prognostic model. Using bioinformatics methods, we predicted the relevant signaling pathways of liver ischemia-reperfusion and key genes. We also evaluated the association of RNA binding protein with immune cell infiltration. Single cell sequencing datasets were used to explore the expression profiles of key genes at the single cell level. Machine learning algorithm is used to predict key gene RNA binding domains.

Results

ROC (Receiver Operating Characteristic) and DCA (Decision Curve Analysis) curves showed that the above diagnostic model had good and stable diagnostic efficacy and clinical practicability. We identified three key genes (BTG2, CCNL1 and DNAJB1) in liver ischemia-reperfusion. DNAJB1, BTG2 and CCNL1 are mainly expressed in immune cells such as macrophages and T cells, and are closely related to inflammatory pathways such as TNF-α, highlighting their importance in hepatic ischemia reperfusion. We identified RNA-binding domains of the above three genes. We found that the expression of DNAJB1, CCNL1 and BTG2 in the ischemia-reperfusion group were significantly higher than those in the sham operation group.

Conclusion

Our study revealed the importance of the candidate RNA binding protein in liver ischemia reperfusion injury and provided new insights into the therapeutic of hepatic ischemia-reperfusion injury.

TLR4 signalling in ischemia/reperfusion injury: a promising target for linking inflammation, oxidative stress and programmed cell death to improve organ transplantation outcomes

Transplantations represent the principal therapeutic interventions for terminal organ failure, a procedure that has salvaged myriad lives annually. Ischemia/reperfusion injury (IRI) is frequently correlated with an unfavourable prognosis and is relevant for early graft dysfunction and graft survival. IRI constitutes a complex pathological state influenced by a series of factors such as oxidative stress, metabolic stress, leukocytic infiltration, programmed cell death pathways, and inflammatory immune responses. Reducing ischemia/reperfusion injury is one of the main directions of transplantation research. Toll-like receptors (TLRs) are important pattern-recognition receptors expressed on various organs that orchestrate the immune responses upon recognising PAMPs and DAMPs. Targeting the TLR4 signalling has recently been suggested as a promising approach for alleviating IRI by affecting inflammation, oxidative stress and programmed cell death (PCD). In this minireview, we summarise the role of TLR4 signalling in regulating inflammation, oxidative stress and PCD in organ transplantation and discuss their interactions during IRI. A detailed understanding of the multiple functions of TLR4 in IRI provides novel insights into developing therapies to improve organ transplantation outcomes.

Crocetin preconditioning attenuates ischemia reperfusion-induced hepatic injury by disrupting Keap1/Nrf2 interaction and activating Nrf2/HO-1 pathway

BACKGROUND

Ischemia reperfusion (I/R) injury is a frequent occurrence during liver transplantation surgery, resulting from the temporary cessation of blood flow and subsequent restoration of blood flow. Serious I/R injury is a significant factor causing transplant failure. Hepatic I/R process is characterized by excessive inflammation, oxidation, and apoptosis. Crocetin (Crt) is a natural compound exhibiting beneficial roles in various I/R-induced organ damages. However, Crt's potential role in hepatic I/R remains unexplored.

OBJECTIVE AND METHODS

In order to reveal the impact of Crt on hepatic I/R and the associated signaling pathway, we utilized a syngeneic orthotopic liver transplantation rat model to induce hepatic I/R injury.

RESULTS

Pretreatment with Crt significantly mitigated hepatic I/R injury. This was evident by decreased activities of serum ALT, AST and LDH, indicating improved liver function. Crt treatment also alleviated oxidative stress, as demonstrated by decreased serum MDA content and elevated serum SOD and GSH-Px activities. Furthermore, Crt suppressed inflammatory responses by downregulating both the serum and liver IL-1β, IL-6 and TNF-α while upregulating IL-10 expression. Additionally, Crt reduced apoptosis by decreasing pro-apoptotic Bax, cleaved caspase-3 and cleaved caspase-9, while increasing anti-apoptotic Bcl2 expression. Notably, these protective effects of Crt were dose-dependent. Moreover, our data indicates that Crt plays protective functions during hepatic I/R via disrupting Keap1/Nrf2 interaction and activating Nrf2/HO-1 signaling. This was further supported by observations of alleviated hepatic histopathological changes in I/R rats treated with Crt.

CONCLUSIONS

Crt shows potential as a therapeutic agent for preventing hepatic I/R injury during clinical liver transplantation.

Targeting NF-κB in Hepatic Ischemia-Reperfusion Alleviation: from Signaling Networks to Therapeutic Targeting

Hepatic ischemia-reperfusion injury (HIRI) is a major complication of liver trauma, resection, and transplantation that can lead to liver dysfunction and failure. Scholars have proposed a variety of liver protection methods aimed at reducing ischemia-reperfusion damage, but there is still a lack of effective treatment methods, which urgently needs to find new effective treatment methods for patients. Many studies have reported that signaling pathway plays a key role in HIRI pathological process and liver function recovery mechanism, among which nuclear transfer factor-κB (NF-κB) signaling pathway is one of the signal transduction closely related to disease. NF-κB pathway is closely related to HIRI pathologic process, and inhibition of this pathway can delay oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction. In addition, NF-κB can also interact with PI3K/Akt, MAPK, and Nrf2 signaling pathways to participate in HIRI regulation. Based on the role of NF-κB pathway in HIRI, it may be a potential target pathway for HIRI. This review emphasizes the role of inhibiting the NF-κB signaling pathway in oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction in HIRI, as well as the effects of related drugs or inhibitors targeting NF-κB on HIRI. The objective of this review is to elucidate the role and mechanism of NF-κB pathway in HIRI, emphasize the important role of NF-κB pathway in the prevention and treatment of HIRI, and provide a theoretical basis for the target NF-κB pathway as a therapy for HIRI.

Inflammatory setting, therapeutic strategies targeting some pro-inflammatory cytokines and pathways in mitigating ischemia/reperfusion-induced hepatic injury: a comprehensive review

Ischemia/reperfusion injury (IRI) is a key determining agent in the pathophysiology of clinical organ dysfunction. It is characterized by an aseptic local inflammatory reaction due to a decrease in blood supply, hence deprivation of dependent oxygen and nutrients. In instances of liver transplantation, this injury may have irreversible implications, resulting in eventual organ rejection. The deterioration associated with IRI is affected by the hepatic health status and various factors such as alterations in metabolism, oxidative stress, and pro-inflammatory cytokines. The primary cause of inflammation is the initial immune response of pro-inflammatory cytokines, while Kupffer cells (KFCs) and neutrophil-produced chemokines also play a significant role. Upon reperfusion, the activation of inflammatory responses can elicit further cellular damage and organ dysfunction. This review discusses the interplay between chemokines, pro-inflammatory cytokines, and other inflammatory mediators that contribute to the damage to hepatocytes and liver failure in rats following IR. Furthermore, it delves into the impact of anti-inflammatory therapies in safeguarding against liver failure and hepatocellular damage in rats following IR. This review investigates the correlation between cytokine factors and liver dysfunction via examining databases, such as PubMed, Google Scholar, Science Direct, Egyptian Knowledge Bank (EKB), and Research Gate.

Predicting mitophagy-related genes and unveiling liver endothelial cell heterogeneity in hepatic ischemia-reperfusion injury

Background

Hepatic Ischemia-Reperfusion Injury (HIRI) is a major complication in liver transplants and surgeries, significantly affecting postoperative outcomes. The role of mitophagy, essential for removing dysfunctional mitochondria and maintaining cellular balance, remains unclear in HIRI.

Methods

To unravel the role of mitophagy-related genes (MRGs) in HIRI, we assembled a comprehensive dataset comprising 44 HIRI samples alongside 44 normal control samples from the Gene Expression Omnibus (GEO) database for this analysis. Using Random Forests and Support Vector Machines - Recursive Feature Elimination (SVM-RFE), we pinpointed eight pivotal genes and developed a logistic regression model based on these findings. Further, we employed consensus cluster analysis for classifying HIRI patients according to their MRG expression profiles and conducted weighted gene co-expression network analysis (WGCNA) to identify clusters of genes that exhibit high correlation within different modules. Additionally, we conducted single-cell RNA sequencing data analysis to explore insights into the behavior of MRGs within the HIRI.

Results

We identified eight key genes (FUNDC1, VDAC1, MFN2, PINK1, CSNK2A2, ULK1, UBC, MAP1LC3B) with distinct expressions between HIRI and controls, confirmed by PCR validation. Our diagnostic model, based on these genes, accurately predicted HIRI outcomes. Analysis revealed a strong positive correlation of these genes with monocytic lineage and a negative correlation with B and T cells. HIRI patients were divided into three subclusters based on MRG profiles, with WGCNA uncovering highly correlated gene modules. Single-cell analysis identified two types of endothelial cells with different MRG scores, indicating their varied roles in HIRI.

Conclusions

Our study highlights the critical role of MRGs in HIRI and the heterogeneity of endothelial cells. We identified the macrophage migration inhibitory factor (MIF) and cGAS-STING (GAS) pathways as regulators of mitophagy's impact on HIRI. These findings advance our understanding of mitophagy in HIRI and set the stage for future research and therapeutic developments.

Breaking distance barriers in liver transplantation: Risk factors and outcomes of long-distance liver grafts

BACKGROUND

Long-distance-traveling liver grafts in liver transplantation present challenges due to prolonged cold ischemic time and increased risk of ischemia-reperfusion injury. We identified long-distance-traveling liver graft donor and recipient characteristics and risk factors associated with long-distance-traveling liver graft use.

METHODS

We conducted a retrospective analysis of data from donor liver transplantation patients registered from 2014 to 2020 in the United Network for Organ Sharing registry database. Donor, recipient, and transplant factors of graft survival were compared between short-travel grafts and long-distance-traveling liver grafts (traveled >500 miles).

RESULTS

During the study period, 28,265 patients received a donation after brainstem death liver transplantation and 3,250 a donation after circulatory death liver transplantation. The long-distance-traveling liver graft rate was 6.2% in donation after brainstem death liver transplantation and 7.1% in donation after circulatory death liver transplantation. The 90-day graft survival rates were significantly worse for long-distance-traveling liver grafts (donation after brainstem death: 95.7% vs 94.5%, donation after circulatory death: 94.5% vs 93.9%). The 3-year graft survival rates were similar for long-distance-traveling liver grafts (donation after brainstem death: 85.5% vs 85.1%, donation after circulatory death: 81.0% vs 80.4%). Cubic spline regression analyses revealed that travel distance did not linearly worsen the prognosis of 3-year graft survival. On the other hand, younger donor age, lower donor body mass index, and shorter cold ischemic time mitigated the negative impact of 90-day graft survival in long-distance-traveling liver grafts.

CONCLUSION

The use of long-distance-traveling liver grafts negatively impacts 90-day graft survival but not 3-year graft survival. Moreover, long-distance-traveling liver grafts are more feasible with appropriate donor and recipient factors offsetting the extended cold ischemic time. Mechanical perfusion can improve long-distance-traveling liver graft use. Enhanced collaboration between organ procurement organizations and transplant centers and optimized transportation systems are essential for increasing long-distance-traveling liver graft use, ultimately expanding the donor pool.

Interplay Between Inflammatory-immune and Interleukin-17 Signalings Plays a Cardinal Role on Liver Ischemia-reperfusion Injury-Synergic Effect of IL-17Ab, Tacrolimus and ADMSCs on Rescuing the Liver Damage

BACKGROUND

This study tested the hypothesis that inflammatory and interleukin (IL)-17 signalings were essential for acute liver ischemia (1 h)-reperfusion (72 h) injury (IRI) that was effectively ameliorated by adipose-derived mesenchymal stem cells (ADMSCs) and tacrolimus.

METHODS

Adult-male SD rats (n = 50) were equally categorized into groups 1 (sham-operated-control), 2 (IRI), 3 [IRI + IL-17-monoclonic antibody (Ab)], 4 (IRI + tacrolimus), 5 (IRI + ADMSCs) and 6 (IRI + tacrolimus-ADMSCs) and liver was harvested at 72 h.

RESULTS

The main findings included: (1) circulatory levels: inflammatory cells, immune cells, and proinflammatory cytokines as well as liver-damage enzyme at the time point of 72 h were highest in group 2, lowest in group 1 and significantly lower in group 6 than in groups 3 to 5 (all p < 0.0001), but they did not differ among these three latter groups; (2) histopathology: the liver injury score, fibrosis, inflammatory and immune cell infiltration in liver immunity displayed an identical pattern of inflammatory cells among the groups (all p < 0.0001); and (3) protein levels: upstream and downstream inflammatory signalings, oxidative-stress, apoptotic and mitochondrial-damaged biomarkers exhibited an identical pattern of inflammatory cells among the groups (all p < 0.0001).

CONCLUSION

Our results obtained from circulatory, pathology and molecular-cellular levels delineated that acute IRI was an intricate syndrome that elicited complex upstream and downstream inflammatory and immune signalings to damage liver parenchyma that greatly suppressed by combined tacrolimus and ADMSCs therapy.

Ghrelin protects against ischemia/reperfusion-induced hepatic injury via inhibiting Caspase-11-mediated noncanonical pyroptosis

BACKGROUND

Ischemia/reperfusion (I/R) injury is a complication of liver transplantation. I/R-induced inflammatory cell death, namely, pyroptosis, that is triggered by overactive inflammasomes results in the production of proinflammatory cytokines. Hepatic I/R injury correlates with the activation of the Caspase-11-mediated pyroptosis pathway. We investigated whether ghrelin, which is a pleiotropic gut hormone, may have anti-hepatic I/R injury effects, but the mechanism by which Ghrelin ameliorates hepatic I/R -induced injury remains a mystery.

METHODS

Hepatic I/R injury was induced in a mouse model by clamping the left and right lobes of the liver for 90 min followed by reperfusion for 6 h, 12 h, or 24 h. As treatment, a saline with or without ghrelin was infused via the tail vain. Hepatocytes were isolated using a two-step collagenase liver perfusion method.

RESULTS

In our study, treatment with ghrelin protected against hepatic I/R injury as shown by decreased alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels (p < 0.001) and reduced the histological injury in liver tissues compared with untreated controls. The LDH level of primary hepatocytes was increased by hypoxia/reoxygenation (H/R), and it was then restored to normal levels by ghrelin-treatment (p < 0.05). Western blotting analysis showed that ghrelin significantly inhibited the expression of pyroptosis-related proteins, including Caspase-11, GSDMD-N, NLRP3 and HMGB1, both in vivo and in vitro (all p < 0.05) compared with the untreated controls. Immunofluorescence showed that the expression of Gasdamin D (GSDMD) in hepatocytes was increased after I/R or H/R, whereas GSDMD expression was reduced by ghrelin treatment (p < 0.05).

CONCLUSIONS

Our findings suggest that ghrelin ameliorated I/R-induced hepatic injury by inhibiting Caspase-11-mediated pyroptosis. Ghrelin may be a potential therapeutic option to prevent hepatic I/R injury after liver transplantation.

Development and Recovery of Liver Injury in Piglets by Incremental Injection of LPS

This study aimed to explore the effects of the incremental injection of lipopolysaccharide (LPS) on liver histopathology, inflammation, oxidative status, and mitochondrial function in piglets. Forty healthy Duroc × Landrace × Yorkshire castrated boars (21 ± 2 days old, weight 6.84 ± 0.11 kg) were randomly assigned to five groups (n = 8) and then slaughtered on days 0 (group 0, without LPS injection), 1 (group 1), 5 (group 5), 9 (group 9), and 15 (group 15) of LPS injection, respectively. The results showed that, compared to the piglets without LPS injection, LPS injection caused liver injury in the early phase, as manifested by the increased activities of serum liver injury-related parameters (aspartate amino transferase, alanine aminotransferase, alkaline phosphatase, cholinesterase, and total bile acid) on day 1, and impaired liver morphology (disordered hepatic cell cord arrangement, dissolved and vacuolized hepatocytes, karyopycnosis, and inflammatory cell infiltration and congestion) on days 1 and 5. Meanwhile, LPS injection caused liver inflammation, oxidative stress, and mitochondrial dysfunction on days 1 and 5, as reflected by the upregulated mRNA expression of TNF-α, IL-6, IL-1β, TLR4, MyD88, and NF-κB; increased MPO and MDA content; and impaired mitochondrial morphology. However, these parameters were ameliorated in the later phase (days 9~15). Taken together, our data indicate that the incremental injection of the LPS-induced liver injury of piglets could be self-repaired.

Bioinformatics analysis of genes related to ferroptosis in hepatic ischemia-reperfusion injury

Background: Primary liver cancer is the sixth most commonly diagnosed cancer and the third leading cause of cancer death worldwide in 2020, and it ranks fifth in global incidence. Liver resection or liver transplantation are the two most prominent surgical procedures for treating primary liver cancer. Both inevitably result in HIRI, causing severe complications for patients and affecting their prognosis and quality of survival. Ferroptosis, a newly discovered mode of cell death, is closely related to HIRI. We used bioinformatics analysis to explore the relationship between the two further. Methods: The GEO database dataset GSE112713 and the FerrDB database data were selected to use bioinformatic analysis methods (difference analysis, FRGs identification, GO analysis, KEGG analysis, PPI network construction and analysis, Hub gene screening with GO analysis and KEGG analysis, intergenic interaction prediction, drug-gene interaction prediction, miRNA prediction) for both for correlation analysis. The GEO database dataset GSE15480 was selected for preliminary validation of the screened Hub genes. Results: We analysed the dataset GSE112713 for differential gene expression before and after hepatic ischemia-reperfusion and identified by FRGs, yielding 11 genes. These 11 genes were subjected to GO, and KEGG analyses, and PPI networks were constructed and analysed. We also screened these 11 genes again to obtain 5 Hub genes and performed GO analysis, KEGG analysis, intergenic interaction prediction, drug-gene interaction prediction, and miRNA prediction on these 5 Hub genes. Finally, we obtained preliminary validation of all these 5 Hub genes by dataset GSE15480. Conclusion: There is a close relationship between HIRI and ferroptosis, and inhibition of ferroptosis can potentially be a new approach to mitigate HIRI treatment in the future.

Anti-inflammatory effects of oral and intraperitoneal administration of cerium oxide nanoparticles on experimental hepatic ischemia-reperfusion injury

Objectives

Hepatic ischemia-reperfusion (IR) injury occurs in liver surgery, resection, and transplantation. Reactive oxygen species (ROS) produced following IR starts the cascade of cell damage, necrosis/apoptosis, and proinflammatory responses by activating intracellular signaling cascade to drive hepatocellular damage. Cerium oxide nanoparticles (CONPs) act as anti-inflammatory and antioxidant agents. Thus, we evaluated the protective effects of oral (o.g.) and intraperitoneal (i.p.) administration of CONPs on hepatic IR injury.

Material and Methods

Mice were randomly divided into five groups: control, sham, IR protocol, CONP+IR (i.p.), and CONP+IR (o.g.). Mouse hepatic IR protocol was applied to the animals in the IR group. CONPs (300 μg/kg) were administered 24 hours before IR protocol. Blood and tissue samples were taken after the reperfusion period.

Results

Hepatic IR injury markedly increased enzyme activities, tissue lipid peroxidation, myeloperoxidase (MPO), xanthine oxidase (XO), nitrite oxide (NO), and tissue nuclear factor kappa-B (NF-κB) p65 levels, plasma pro-inflammatory cytokines, chemokines, and adhesion molecules while decreasing antioxidant markers and caused pathological changes in hepatic tissue. The expression of tumor necrosis factor alpha (TNF-α), matrix metalloproteinase 2 (MMP-2), and 9 increased, and tissue inhibitor matrix metalloproteinase 1 (TIMP-1) expression decreased in the IR group. Pretreatment with CONPs o.g. and i.p. 24 hours before hepatic ischemia improved the biochemical parameters above and alleviated the histopathological findings.

Conclusion

Results of the present study demonstrate a significant reduction in liver degeneration by administering CONPs via i.p. and o.g. route in an experimental liver IR model, suggesting that CONPs have the extensive potential to prevent hepatic IR injury.

NOD1 induces pyroptotic cell death to aggravate liver ischemia-reperfusion injury in mice

Nucleotide-binding oligomerization domain 1 (NOD1) can direct the release of inflammatory factors and influence autophagy and apoptosis in hepatic ischemia-reperfusion injury (IRI) in mice. As pyroptosis is involved in a number of inflammatory reactions, in this report, we investigated the potential for NOD1 to affect pyroptosis. We found that an increased expression of NOD1 during IRI was related to activation of the pyroptotic signaling pathway. With NOD1 activation, cleavage fragments of Caspase-1, gasdermin D (GSDMD), and interleukin (IL)-1β were all increased. Moreover, downregulation of NOD1 expression in AML12 cells exerted an opposite effect. Expression levels of cleaved-Caspase-1 and cleaved-GSDMD decreased after exposure to IRI and the number of cell membrane pores and apoptotic or pyroptotic cells decreased, along with the contents of inflammatory factors and lactate dehydrogenase in the supernatants of AML12 cells. Based on these findings, we conclude that NOD1 aggravates the pyroptotic cell death associated with hepatic ischemia-reperfusion injury in a mouse model via the Caspase-1/GSDMD axis. These findings help to alleviate pyroptotic cell death during liver transplantation or resection, providing new insights into novel protective therapies for liver IRI.

Effects of Dexmedetomidine Administered Through Different Routes on Kidney Tissue in Rats with Spinal Cord Ischaemia–Reperfusion Injury

Background

Ischaemia–reperfusion (IR) injury, which can be encountered during surgical procedures involving the abdominal aorta, is a complex process that affects distant organs, such as the heart, liver, kidney, and lungs, as well as the lower extremities. In this study, we aimed to contribute to the limited literature by investigating the protective effect of dexmedetomidine, which was administered through different routes, on kidney tissue in rats with spinal cord IR injury.

Methods

A total of 30 rats were randomly divided into five groups: control (C group), IR (IR group), IR-intraperitoneal dexmedetomidine (IRIPD group), IR-intrathecal dexmedetomidine (IRITD group), and IR-intravenous dexmedetomidine (IRIVD group). The spinal cord IR model was established. Dexmedetomidine was administered at doses of 100 µg/kg intraperitoneally, 3 µg/kg intrathecally, and 9 µg/kg intravenously. Histopathologic parameters in kidney tissue samples taken at the end of the reperfusion period and biochemical parameters in serum were evaluated.

Results

When examined histopathologically, tubular dilatation was found to be significantly reduced in the IRIVD, IRITD, and IRIPD groups compared with the IR group (p = 0.012, all). Vascular vacuolization and hypertrophy were significantly decreased in the IRIVD, IRITD, and IRIPD groups compared with the IR group (p = 0.006, all). Tubular cell degeneration and necrosis were significantly reduced in the IRIVD, IRITD, and IRIPD groups compared with the IR group (p = 0.008, p = 0.08, and p = 0.030, respectively). Lymphocyte infiltration was significantly decreased in the IRIVD and IRITD groups compared with the IR group (p = 0.006 and p = 0.06, respectively).

Conclusion

It was observed that dexmedetomidine administered by different routes improved the damage caused by IR in kidney histopathology. We think that the renoprotective effects of dexmedetomidine administered intravenously and intrathecally before IR in rats are greater.

Type 1 Innate Lymphoid Cells Are Proinflammatory Effector Cells in Ischemia-Reperfusion Injury of Steatotic Livers

Innate lymphoid cells (ILCs), the most recently described family of lymphoid cells, play fundamental roles in tissue homeostasis through the production of key cytokine. Group 1 ILCs, comprised of conventional natural killer cells (cNKs) and type 1 ILCs (ILC1s), have been implicated in regulating immune-mediated inflammatory diseases. However, the role of ILC1s in nonalcoholic fatty liver disease (NAFLD) and ischemia-reperfusion injury (IRI) is unclear. Here, we investigated the role of ILC1 and cNK cells in a high-fat diet (HFD) murine model of partial warm IRI. We demonstrated that hepatic steatosis results in more severe IRI compared to non-steatotic livers. We further elicited that HFD-IRI mice show a significant increase in the ILC1 population, whereas the cNK population was unchanged. Since ILC1 and cNK are major sources of IFN-γ and TNF-α, we measured the level of ex vivo cytokine expression in normal diet (ND)-IRI and HFD-IRI conditions. We found that ILC1s in HFD-IRI mice produce significantly more IFN-γ and TNF-α when compared to ND-IRI. To further assess whether ILC1s are key proinflammatory effector cells in hepatic IRI of fatty livers, we studied both Rag1−/− mice, which possess cNK cells, and a substantial population of ILC1s versus the newly generated Rag1−/−Tbx21−/− double knockout (Rag1-Tbet DKO) mice, which lack type 1 ILCs, under HFD IRI conditions. Importantly, HFD Rag1-Tbet DKO mice showed significant protection from hepatic injury upon IRI when compared to Rag1−/− mice, suggesting that T-bet-expressing ILC1s play a role, at least in part, as proinflammatory effector cells in hepatic IRI under steatotic conditions.

The Fatal Circle of NETs and NET-Associated DAMPs Contributing to Organ Dysfunction

The innate immune system is the first line of defense against invading pathogens or sterile injuries. Pattern recognition receptors (PRR) sense molecules released from inflamed or damaged cells, or foreign molecules resulting from invading pathogens. PRRs can in turn induce inflammatory responses, comprising the generation of cytokines or chemokines, which further induce immune cell recruitment. Neutrophils represent an essential factor in the early immune response and fulfill numerous tasks to fight infection or heal injuries. The release of neutrophil extracellular traps (NETs) is part of it and was originally attributed to the capture and elimination of pathogens. In the last decade studies revealed a detrimental role of NETs during several diseases, often correlated with an exaggerated immune response. Overwhelming inflammation in single organs can induce remote organ damage, thereby further perpetuating release of inflammatory molecules. Here, we review recent findings regarding damage-associated molecular patterns (DAMPs) which are able to induce NET formation, as well as NET components known to act as DAMPs, generating a putative fatal circle of inflammation contributing to organ damage and sequentially occurring remote organ injury.

Liver Ischemia and Reperfusion Induce Periportal Expression of Necroptosis Executor pMLKL Which Is Associated With Early Allograft Dysfunction After Transplantation

Background

Early allograft dysfunction (EAD) following liver transplantation (LT) remains a major threat to the survival of liver grafts and recipients. In animal models, it is shown that hepatic ischemia-reperfusion injury (IRI) triggers phosphorylation of Mixed Lineage Kinase domain-like protein (pMLKL) inducing necroptotic cell death. However, the clinical implication of pMLKL-mediated cell death in human hepatic IRI remains largely unexplored. In this study, we aimed to investigate the expression of pMLKL in human liver grafts and its association with EAD after LT.

Methods

The expression of pMLKL was determined by immunohistochemistry in liver biopsies obtained from both human and rat LT. Human liver biopsies were obtained at the end of preservation (T0) and ~1 hour after reperfusion (T1). The positivity of pMLKL was quantified electronically and compared in rat and human livers and post-LT outcomes. Multiplex immunofluorescence staining was performed to characterize the pMLKL-expressing cells.

Results

In the rat LT model, significant pMLKL expression was observed in livers after IRI as compared to livers of sham-operation animals. Similarly, the pMLKL score was highest after IRI in human liver grafts (in T1 biopsies). Both in rats and humans, the pMLKL expression is mostly observed in the portal triads. In grafts who developed EAD after LT (n=24), the pMLKL score at T1 was significantly higher as compared to non-EAD grafts (n=40). ROC curve revealed a high predictive value of pMLKL score at T1 (AUC 0.70) and the ratio of pMLKL score at T1 and T0 (pMLKL-index, AUC 0.82) for EAD. Liver grafts with a high pMLKL index (>1.64) had significantly higher levels of serum ALT, AST, and LDH 24 hours after LT compared to grafts with a low pMLKL index. Multivariate logistical regression analysis identified the pMLKL-index (Odds ratio=1.3, 95% CI 1.1-1.7) as a predictor of EAD development. Immunohistochemistry on serial sections and multiplex staining identified the periportal pMLKL-positive cells as portal fibroblasts, fibrocytes, and a minority of cholangiocytes.

Conclusion

Periportal pMLKL expression increased significantly after IRI in both rat and human LT. The histological score of pMLKL is predictive of post-transplant EAD and is associated with early liver injury after LT. Periportal non-parenchymal cells (i.e. fibroblasts) appear most susceptible to pMLKL-mediated cell death during hepatic IRI.

Hypoxic/Ischemic Inflammation, MicroRNAs and δ-Opioid Receptors: Hypoxia/Ischemia-Sensitive Versus-Insensitive Organs

Hypoxia and ischemia cause inflammatory injury and critically participate in the pathogenesis of various diseases in various organs. However, the protective strategies against hypoxic and ischemic insults are very limited in clinical settings up to date. It is of utmost importance to improve our understanding of hypoxic/ischemic (H/I) inflammation and find novel therapies for better prevention/treatment of H/I injury. Recent studies provide strong evidence that the expression of microRNAs (miRNAs), which regulate gene expression and affect H/I inflammation through post-transcriptional mechanisms, are differentially altered in response to H/I stress, while δ-opioid receptors (DOR) play a protective role against H/I insults in different organs, including both H/I-sensitive organs (e.g., brain, kidney, and heart) and H/I-insensitive organs (e.g., liver and muscle). Indeed, many studies have demonstrated the crucial role of the DOR-mediated cyto-protection against H/I injury by several molecular pathways, including NLRP3 inflammasome modulated by miRNAs. In this review, we summarize our recent studies along with those of others worldwide, and compare the effects of DOR on H/I expression of miRNAs in H/I-sensitive and -insensitive organs. The alternation in miRNA expression profiles upon DOR activation and the potential impact on inflammatory injury in different organs under normoxic and hypoxic conditions are discussed at molecular and cellular levels. More in-depth investigations into this field may provide novel clues for new protective strategies against H/I inflammation in different types of organs.

Necroptosis in Solid Organ Transplantation: A Literature Overview

Ischemia-reperfusion injury (IRI) is encountered in various stages during solid organ transplantation (SOT). IRI is known to be a multifactorial inflammatory condition involving hypoxia, metabolic stress, leukocyte extravasation, cellular death (including apoptosis, necrosis and necroptosis) and an activation of immune response. Although the cycle of sterile inflammation during IRI is consistent among different organs, the underlying mechanisms are poorly understood. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be crucial in the implementation of necroptosis. Moreover, apart from “silent” apoptotic death, necrosis also causes sterile inflammation—necroinflammation, which is triggered by various damage-associated molecular patterns (DAMPs). Those DAMPs activate the innate immune system, causing local and systemic inflammatory responses, which can result in graft failure. In this overview we summarize knowledge on mechanisms of sterile inflammation processes during SOT with special focus on necroptosis and IRI and discuss protective strategies.

Does Arterialization of Portal Vein Have Any Effects in Large-for-Size Liver Transplantation? Hemodynamic, Histological, and Biomolecular Experimental Studies

BACKGROUND

In pediatric liver transplantation, the optimal size of the transplanted liver ranges between 0.8% and 4.0% of the recipient's weight. Sometimes, the graft weight exceeds this upper limit, characterizing the large-for-size condition potentially associated with reduced blood flow and worsening of ischemia-reperfusion injury. Therefore, it would be beneficial to increase the portal flow through arterialization of the portal vein. Materials and methods: Fifteen pigs underwent large-for-size liver transplants. They were divided into two groups: control (CTRL 6 animals - conventional technique) and arterialization - a shunt was established between the portal vein and the splenic artery (ART 9 animals). Hemodynamic, biochemical, histological, and molecular variables were compared. Results: Arterialization resulted in a significant increase in portal vein pressure but no changes in other hemodynamic variables, as shown in the analysis of variance. It was observed lower ALT values (p = 0.007), with no differences regarding the values of blood pH and lactate (p = 0.54 and p = 0.699 respectively) or histological variables (edema, steatosis, inflammation, necrosis, and IRI - p = 1.0, p = 0.943, p = 0.174, p = 0.832, p = 0.662, respectively). The molecular studies showed significantly increased expression of IL6 after 3 hours of reperfusion (p = 0.048) and decreased expression of ICAM immediately after reperfusion (p = 0.03). The regression analysis suggested a positive influence of portal flow and pressure on biochemical parameters. Conclusion: Arterialization of the portal vein showed no histological, biochemical, or molecular benefits in large-for-size transplantation.

Mitochondrial Dysfunction and Oxidative Stress in Liver Transplantation and Underlying Diseases: New Insights and Therapeutics

Mitochondria are essential organelles for cellular energy and metabolism. Like with any organ, the liver highly depends on the function of these cellular powerhouses. Hepatotoxic insults often lead to an impairment of mitochondrial activity and an increase in oxidative stress, thereby compromising the metabolic and synthetic functions. Mitochondria play a critical role in ATP synthesis and the production or scavenging of free radicals. Mitochondria orchestrate many cellular signaling pathways involved in the regulation of cell death, metabolism, cell division, and progenitor cell differentiation. Mitochondrial dysfunction and oxidative stress are closely associated with ischemia-reperfusion injury during organ transplantation and with different liver diseases, including cholestasis, steatosis, viral hepatitis, and drug-induced liver injury. To develop novel mitochondria-targeting therapies or interventions, a better understanding of mitochondrial dysfunction and oxidative stress in hepatic pathogenesis is very much needed. Therapies targeting mitochondria impairment and oxidative imbalance in liver diseases have been extensively studied in preclinical and clinical research. In this review, we provide an overview of how oxidative stress and mitochondrial dysfunction affect liver diseases and liver transplantation. Furthermore, we summarize recent developments of antioxidant and mitochondria-targeted interventions.

Regulation of autophagy protects against liver injury in liver surgery-induced ischaemia/reperfusion

Transient ischaemia and reperfusion in liver tissue induce hepatic ischaemia/reperfusion (I/R) tissue injury and a profound inflammatory response in vivo. Hepatic I/R can be classified into warm I/R and cold I/R and is characterized by three main types of cell death, apoptosis, necrosis and autophagy, in rodents or patients following I/R. Warm I/R is observed in patients or animal models undergoing liver resection, haemorrhagic shock, trauma, cardiac arrest or hepatic sinusoidal obstruction syndrome when vascular occlusion inhibits normal blood perfusion in liver tissue. Cold I/R is a condition that affects only patients who have undergone liver transplantation (LT) and is caused by donated liver graft preservation in a hypothermic environment prior to entering a warm reperfusion phase. Under stress conditions, autophagy plays a critical role in promoting cell survival and maintaining liver homeostasis by generating new adenosine triphosphate (ATP) and organelle components after the degradation of macromolecules and organelles in liver tissue. This role of autophagy may contribute to the protection of hepatic I/R‐induced liver injury; however, a considerable amount of evidence has shown that autophagy inhibition also protects against hepatic I/R injury by inhibiting autophagic cell death under specific circumstances. In this review, we comprehensively discuss current strategies and underlying mechanisms of autophagy regulation that alleviates I/R injury after liver resection and LT. Directed autophagy regulation can maintain liver homeostasis and improve liver function in individuals undergoing warm or cold I/R. In this way, autophagy regulation can contribute to improving the prognosis of patients undergoing liver resection or LT.

Resolving the graft ischemia-reperfusion injury during liver transplantation at the single cell resolution

Ischemia–reperfusion injury (IRI) remains the major reason for impaired donor graft function and increased mortality post-liver transplantation. The mechanism of IRI involves multiple pathophysiological processes and numerous types of cells. However, a systematic and comprehensive single-cell transcriptional profile of intrahepatic cells during liver transplantation is still unclear. We performed a single-cell transcriptome analysis of 14,313 cells from liver tissues collected from pre-procurement, at the end of preservation and 2 h post-reperfusion. We made detailed annotations of mononuclear phagocyte, endothelial cell, NK/T, B and plasma cell clusters, and we described the dynamic changes of the transcriptome of these clusters during IRI and the interaction between mononuclear phagocyte clusters and other cell clusters. In addition, we found that TNFAIP3 interacting protein 3 (TNIP3), specifically and highly expressed in Kupffer cell clusters post-reperfusion, may have a protective effect on IRI. In summary, our study provides the first dynamic transcriptome map of intrahepatic cell clusters during liver transplantation at single-cell resolution.

Hepatic ischemia reperfusion injury: effect of moderate intensity exercise and oxytocin compared to l-arginine in a rat model

Background

Hepatic ischemia reperfusion (IR) injury is considered as a main cause of liver damage and dysfunction. The l-arginine/nitric oxide pathway seems to be relevant during this process of IR. Although acute intense exercise challenges the liver with increased reactive oxygen species (ROS), regular training improves hepatic antioxidant status. Also, oxytocin (Oxy), besides its classical functions, it exhibits a potent antistress, anti-inflammatory, and antioxidant effects. This study was designed to evaluate the hepatic functional and structural changes induced by hepatic IR injury in rats and to probe the effect and potential mechanism of moderate intensity exercise training and/or Oxy, in comparison to a nitric oxide donor, l-arginine, against liver IR-induced damage.

Results

Compared to the sham-operated control group, the hepatic IR group displayed a significant increase in serum levels of ALT and AST, plasma levels of MDA and TNF-α, and significant decrease in plasma TAC and nitrite levels together with the worsening of liver histological picture. L-Arg, Oxy, moderate intensity exercise, and the combination of both Oxy and moderate intensity exercises ameliorated these deleterious effects that were evident by the significant decrease in serum levels of ALT and AST, significant elevation in TAC and nitrite, and significant decline in lipid peroxidation (MDA) and TNF-α, besides regression of histopathological score regarding hepatocyte necrosis, vacuolization, and nuclear pyknosis. Both the moderate intensity exercise-trained group and Oxy-treated group showed a significant decline in TNF-α and nitrite levels as compared to l-Arg-treated group. The Oxy-treated group showed statistical insignificant changes in serum levels of ALT, AST, and plasma levels of nitrite, MDA, TAC, and TNF-α as compared to moderate intensity exercise-trained group.

Conclusion

The combination of both moderate intensity exercise and Oxy displayed more pronounced hepatoprotection on comparison with l-Arg which could be attributed to their more prominent antioxidant and anti-inflammatory effects but not due to their NO-enhancing effect.

The Protective Effect of Traditional Chinese Medicine on Liver Ischemia-Reperfusion Injury

Liver ischemia-reperfusion (I/R) injury occurs during transplantation and major hepatic surgery, which may lead to postoperative liver dysfunction. More and more traditional Chinese medicines (TCMs) have been used to treat liver ischemia-reperfusion injury. The purpose of this review is to evaluate the different protective effects of TCMs in the treatment of liver ischemia-reperfusion injury and to summarize its possible mechanisms. The results indicate that TCMs attenuate liver I/R injury via multiple mechanisms, including antioxidation stress, anti-inflammatory response, antiapoptosis, and inhibiting endoplasmic reticulum stress. However, the in-depth mechanism of the protective effects of these traditional Chinese medicines still remains unknown.

Pharmacological properties of baicalin on liver diseases: a narrative review

Baicalin is the main active component of Scutellaria baicalensis, widely used in traditional Chinese medicine thanks to its various pharmacological effects, such as anti-tumor, anti-inflammatory, and antibacterial properties, as well as cardiovascular, hepatic, and renal protective effect. Recently, the protective effects of baicalin on liver disease have received much more attention. Several studies showed that baicalin protects against several types of liver diseases including viral hepatitis, fatty liver disease, xenobiotic induced liver injury, cholestatic liver injury, and hepatocellular carcinoma, with a variety of pharmacological mechanisms. A comprehensive understanding of the mechanism of baicalin can provide a valuable reference for its clinical use, but up to now, no narrative review is available that summarizes the pharmacological effects of baicalin to clarify its potential use in the treatment of liver diseases. Therefore, this review summarizes the progress of baicalin research and the underlying mechanism in the treatment of various liver diseases, to promote further research and its clinical application.

Emerging recognition of the complement system in hepatic ischemia/reperfusion injury, liver regeneration and recovery (Review)

Hepatic ischemia/reperfusion injury (IRI) is a result of the ischemic cascade and may occur in the settings of liver trauma, resection and transplantation. Components of the complement system have been indicated to be mediators of hepatic IRI and regulators of liver regeneration. As such, their potential to mediate both beneficial and harmful effects render them key targets for therapy. In the present study, the mechanisms of complement mediating hepatic IRI were discussed with a focus on the different functions of complement in hepatic injury and liver recovery, and an explanation for this apparent paradox is provided, i.e. that the complement products C3a and C5a have an important role in liver damage; however, C3a and C5a are also necessary for liver regeneration. Furthermore, situated at the end of the complement activation cascade, the membrane attack complex is crucial in hepatic IRI and inhibiting the complex with a site-targeted murine complement inhibitor, complement receptor 2-CD59, may improve liver regeneration after partial hepatectomy, even when hepatectomy is combined with ischemia and reperfusion.

Immune-Responsive Gene 1/Itaconate Activates Nuclear Factor Erythroid 2-Related Factor 2 in Hepatocytes to Protect Against Liver Ischemia-Reperfusion Injury

BACKGROUND AND AIMS

Itaconate, a metabolite of the tricarboxylic acid cycle, plays anti-inflammatory roles in macrophages during endotoxemia. The mechanisms underlying its anti-inflammatory roles have been shown to be mediated by the modulation of oxidative stress, an important mechanism of hepatic ischemia-reperfusion (I/R) injury. However, the role of itaconate in liver I/R injury is unknown.

APPROACH AND RESULTS

We found that deletion of immune-responsive gene 1 (IRG1), encoding for the enzyme producing itaconate, exacerbated liver injury and systemic inflammation. Furthermore, bone marrow adoptive transfer experiments indicated that deletion of IRG1 in both hematopoietic and nonhematopoietic compartments contributes to the protection mediated by IRG1 after I/R. Interestingly, the expression of IRG1 was up-regulated in hepatocytes after I/R and hypoxia/reoxygenation-induced oxidative stress. Modulation of the IRG1 expression levels in hepatocytes regulated hepatocyte cell death. Importantly, addition of 4-octyl itaconate significantly improved liver injury and hepatocyte cell death after I/R. Furthermore, our data indicated that nuclear factor erythroid 2-related factor 2 (Nrf2) is required for the protective effect of IRG1 on mouse and human hepatocytes against oxidative stress-induced injury. Our studies document the important role of IRG1 in the acute setting of sterile injury induced by I/R. Specifically, we provide evidence that the IRG1/itaconate pathway activates Nrf2-mediated antioxidative response in hepatocytes to protect liver from I/R injury.

CONCLUSIONS

Our data expand on the importance of IRG1/itaconate in nonimmune cells and identify itaconate as a potential therapeutic strategy for this unfavorable postsurgical complication.

Anti-Inflammatory and Antioxidant Effect of Eucommia ulmoides Polysaccharide in Hepatic Ischemia-Reperfusion Injury by Regulating ROS and the TLR-4-NF-κB Pathway

Eucommia ulmoides polysaccharide (EUP) has been shown to have anti-inflammatory and antioxidant effects. However, the mechanism underlying these effects has rarely been reported, and whether EUP can reduce liver injury in hepatic ischemia-reperfusion injury (HIRI) has not been reported. In this study, 40 Sprague-Dawley (SD) rats were randomly divided into 5 groups: the sham group, ischemia-reperfusion (I/R) group, and three EUP pretreatment groups (320 mg/kg, 160 mg/kg, and 80 mg/kg). SD rats were pretreated with EUP by gavage once a day prior to I/R injury for 10 days. Except for the sham group, blood flow in the middle and left liver lobes was blocked in all the other groups, resulting in 70% liver ischemia, and the ischemia and reperfusion times were 1 h and 4 h, respectively. Ischemic liver tissue and serum were obtained to detect biochemical markers and liver histopathological damage. Compared with the I/R group, after EUP pretreatment, serum alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor-α, and interleukin-1β levels were significantly decreased, malondialdehyde levels in liver tissues were significantly decreased, superoxide dismutase levels were significantly increased, and the area of liver necrosis was notably reduced. To understand the specific mechanism involved, we determined the levels of Toll-like receptor- (TLR-) 4-nuclear factor-kappaB (NF-κB) pathway-associated proteins in vivo and in vitro. The data showed that EUP can reduce liver damage by decreasing ROS levels and inhibiting TLR-4-NF-κB pathway activation and may be a promising drug in liver surgery to prevent HIRI.

Implications of hydrogen sulfide in liver pathophysiology: Mechanistic insights and therapeutic potential

Background

Over the last several decades, hydrogen sulfide (H₂S) has been found to exert multiple physiological functions in mammal systems. The endogenous production of H₂S is primarily mediated by cystathione β-synthase (CBS), cystathione γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes are widely expressed in the liver tissues and regulate hepatic functions by acting on various molecular targets.

Aim of Review

In the present review, we will highlight the recent advancements in the cellular events triggered by H₂S under liver diseases. The therapeutic effects of H₂S donors on hepatic diseases will also be discussed.

Key Scientific Concepts of Review

As a critical regulator of liver functions, H₂S is critically involved in the etiology of various liver disorders, such as nonalcoholic steatohepatitis (NASH), hepatic fibrosis, hepatic ischemia/reperfusion (IR) injury, and liver cancer. Targeting H₂S-producing enzymes may be a promising strategy for managing hepatic disorders.

Neutrophil Extracellular Traps and Liver Disease

Neutrophil extracellular traps, or NETs, are heterogenous, filamentous structures which consist of extracellular DNA, granular proteins, and histones. NETs are extruded by a neutrophil in response to various stimuli. Although NETs were initially implicated in immune defense, subsequent studies have implicated NETs in a spectrum of disease processes, including autoimmune disease, thrombosis, and cancer. NETs also contribute to the pathogenesis of several common liver diseases, including alcohol-associated liver disease and portal hypertension. Although there is much interest in the therapeutic potential of NET inhibition, future clinical applications must be balanced against potential increased risk of infection.

LncRNA Gm4419 induces cell apoptosis in hepatic ischemia-reperfusion injury via regulating the miR-455-SOX6 axis

Long non-coding RNA (lncRNA) is known to be involved in a variety of diseases. However, the role of Gm4419 in hepatic ischemia-reperfusion (I/R) injury remains unknown. To study this, we first established a rat model of hepatic I/R, and a BRL-3A cell model of hypoxia-reoxygenation (H/R) for in vivo and in vitro studies. Staining with hematoxylin and eosin and hepatic injury scores were used to evaluate the degree of hepatic I/R injury. Cell apoptosis was assessed via staining with Edu, and with annexin V-FITC-propidium iodide assays. The interactions between Gm4419 and miR-455, as well as miR-455 and SOX6 were evaluated via luciferase reporter activity assays and RNA immunoprecipitation assays. In vivo, we found that Gm4419 was up-regulated in the rats subjected to I/R. Moreover, knockdown of Gm4419 alleviated the I/R-induced liver damage in the rats. In vitro, knockdown of Gm4419 alleviated H/R-induced apoptosis in BRL-3A cells. Interestingly, we found that miR-455 is a target of Gm4419, and Gm4419 regulates the expression of miR-455 via sponging. Furthermore, SOX6 was proven to be the target of miR-455. Finally, rescue experiments confirmed that knockdown of Gm4419 inhibits apoptosis by regulating miR-455 and SOX6 in H/R-treated BRL-3A cells. Therefore, our findings show that the lncRNA Gm4419 accelerates hepatic I/R injury by targeting the miR-455-SOX6 axis, which suggests a novel therapeutic target for hepatic I/R injury.

Remote Ischemic Preconditioning and Diazoxide Protect from Hepatic Ischemic Reperfusion Injury by Inhibiting HMGB1-Induced TLR4/MyD88/NF-κB Signaling

Remote ischemic preconditioning (RIPC) is known to have a protective effect against hepatic ischemia-reperfusion (IR) injury in animal models. However, the underlying mechanism of action is not clearly understood. This study examined the effectiveness of RIPC in a mouse model of hepatic IR and aimed to clarify the mechanism and relationship of the ATP-sensitive potassium channel (K_ATP) and HMGB1-induced TLR4/MyD88/NF-κB signaling. C57BL/6 male mice were separated into six groups: (i) sham-operated control, (ii) IR, (iii) RIPC+IR, (iv) RIPC+IR+glyburide (K_ATP blocker), (v) RIPC+IR+diazoxide (K_ATP opener), and (vi) RIPC+IR+diazoxide+glyburide groups. Histological changes, including hepatic ischemia injury, were assessed. The levels of circulating liver enzymes and inflammatory cytokines were measured. Levels of apoptotic proteins, proinflammatory factors (TLR4, HMGB1, MyD88, and NF-κB), and IκBα were measured by Western blot and mRNA levels of proinflammatory cytokine factors were determined by RT-PCR. RIPC significantly decreased hepatic ischemic injury, inflammatory cytokine levels, and liver enzymes compared to the corresponding values observed in the IR mouse model. The K_ATP opener diazoxide + RIPC significantly reduced hepatic IR injury demonstrating an additive effect on protection against hepatic IR injury. The protective effect appeared to be related to the opening of K_ATP, which inhibited HMGB1-induced TRL4/MyD88/NF-kB signaling.

Comparative study on protective effect of hydrogen rich saline and adipose-derived stem cells on hepatic ischemia-reperfusion and hepatectomy injury in swine

AIM

To compare and evaluate the hepatoprotective effect of liver parenchyma injection of ADSCs and portal vein injection of HRS in laparoscopic hepatic ischemia reperfusion combined with hepatectomy injury in miniature pigs.

METHODS

Eighteen miniature pigs were randomly assigned to IRI group, HRS group and ADSCs group. HRS was injected through the portal vein 10 min before reperfusion, 1 d, 2 d, and 3 d after surgery. ADSCs were injected into liver parenchyma after hepatectomy. The serum and liver tissue samples were collected at different time points (preoperative, and postoperative at 1 d, 3 d and 7 d).

RESULTS

Compared with the IRI group, both ADSCs and HRS groups can promote liver function recovery, reduce oxidative stress, reduce inflammation, and promote liver regeneration. Compared with HRS, ALT and TBIL in ADSCs group were significantly decreased at 3 d, and AST was significantly reduced at 1 d. The activities of SOD and GSH-Px in ADSCs group were significantly higher than that in HRS group, but the MDA level in HRS group was markedly lower than that in ADSCs group at 1 d. IL-1β was significantly lower in the ADSCs group than in the HRS group at 1 day after operation. The expressions of HGF and PCNA were significantly higher than that in the HRS group at 3 day after surgery.

CONCLUSION

Our study has demonstrated that HRS and ADSCs have significant hepatoprotective effects in miniature pigs after HIRI and hepatectomy injury. However, liver parenchyma injection of ADSCs is more beneficial to the recovery of liver function than portal vein injection of HRS.

Splenic ischemic preconditioning attenuates oxidative stress induced by hepatic ischemia-reperfusion in rats

Purpose:

To evaluate the effects of splenic ischemic preconditioning (sIPC) on oxidative stress induced by hepatic ischemia-reperfusion in rats.

Methods:

Fifteen male Wistar rats were equally divided into 3 groups: SHAM, IRI and sIPC. Animals from IRI group were subjected to 45 minutes of partial liver ischemia (70%). In the sIPC group, splenic artery was clamped in 2 cycles of 5 min of ischemia and 5 min of reperfusion (20 min total) prior to hepatic ischemia. SHAM group underwent the same surgical procedures as in the remaining groups, but no liver ischemia or sIPC were induced. After 1h, hepatic and splenic tissue samples were harvested for TBARS, CAT, GPx and GSH-Rd measurement.

Results:

sIPC treatment significantly decreased both hepatic and splenic levels of TBARS when compared to IRI group (p<0.01). Furthermore, the hepatic and splenic activities of CAT, GPx and GSH- Rd were significantly higher in sIPC group than in IRI group.

Conclusion:

sIPC was able to attenuate hepatic and splenic IRI-induced oxidative stress.

Necroptotic Cell Death in Liver Transplantation and Underlying Diseases: Mechanisms and Clinical Perspective

Cell death is a natural process for the turnover of aged cells, but it can also arise as a result of pathological conditions. Cell death is recognized as a key feature in both acute and chronic hepatobiliary diseases caused by drug, alcohol, and fat uptake; by viral infection; or after surgical intervention. In the case of chronic disease, cell death can lead to (chronic) secondary inflammation, cirrhosis, and the progression to liver cancer. In liver transplantation, graft preservation and ischemia/reperfusion injury are associated with acute cell death. In both cases, so-called programmed cell death modalities are involved. Several distinct types of programmed cell death have been described of which apoptosis and necroptosis are the most well known. Parenchymal liver cells, including hepatocytes and cholangiocytes, are susceptible to both apoptosis and necroptosis, which are triggered by distinct signal transduction pathways. Apoptosis is dependent on a proteolytic cascade of caspase enzymes, whereas necroptosis induction is caspase-independent. Moreover, different from the "silent" apoptotic cell death, necroptosis can cause a secondary inflammatory cascade, so-called necroinflammation, triggered by the release of various damage-associated molecular patterns (DAMPs). These DAMPs activate the innate immune system, leading to both local and systemic inflammatory responses, which can even cause remote organ failure. Therapeutic targeting of necroptosis by pharmacological inhibitors, such as necrostatin-1, shows variable effects in different disease models.

Up-regulation of FOXO1 and reduced inflammation by β-hydroxybutyric acid are essential diet restriction benefits against liver injury

Liver ischemia and reperfusion injury (IRI) is a major challenge in liver surgery. Diet restriction reduces liver damage by increasing stress resistance; however, the underlying molecular mechanisms remain unclear. We investigated the preventive effect of 12-h fasting on mouse liver IRI. Partial warm hepatic IRI model in wild-type male C57BL/6 mice was used. The control ischemia and reperfusion (IR) group of mice was given food and water ad libitum, while the fasting IR group was given water but not food for 12 h before ischemic insult. In 12-h fasting mice, serum liver-derived enzyme level and tissue damages due to IR were strongly suppressed. Serum β-hydroxybutyric acid (BHB) was significantly raised before ischemia and during reperfusion. Up-regulated BHB induced an increment in the expression of FOXO1 transcription factor by raising the level of acetylated histone. Antioxidative enzyme heme oxigenase 1 (HO-1), a target gene of FOXO1, then increased. Autophagy activity was also enhanced. Serum high-mobility group box 1 was remarkably lowered by the 12-h fasting, and activation of NF-κB and NLRP3 inflammasome was suppressed. Consequently, inflammatory cytokine production and liver injury were reduced. Exogenous BHB administration or histone deacetylase inhibitor administration into the control fed mice ameliorated liver IRI, while FOXO1 inhibitor administration to the 12-h fasting group exacerbated liver IRI. The 12-h fasting exerted beneficial effects on the prevention of liver IRI by increasing BHB, thus up-regulating FOXO1 and HO-1, and by reducing the inflammatory responses and apoptotic cell death via the down-regulation of NF-κB and NLRP3 inflammasome.

Neuroprotective Effects of Tocilizumab on Experimentally-Induced Spinal Cord Ischemia-Reperfusion Injury

OBJECTIVES

We aimed to evaluate neuroprotective effects of tocilizumab on spinal cord ischemia-reperfusion (I/R) injury. Our study design was an experimental rabbit spinal cord I/R injury model, and the setting was at the Animal Research Laboratory, Necmettin Erbakan University, Meram School of Medicine, Konya, Turkey.

METHODS

Twenty-four adult New Zealand rabbits were randomly divided into 3 groups: Group 1, control group (n = 8); Group 2, I/R group, and Group 3 (n = 8) I/R injury + tocilizumab (4 mg/kg, ip) treatment group. Spinal cord I/R injury repair was performed by infrarenal aortic cross clamping. On neurologic evaluation, spinal cord tissue plasma tumor necrosis factor alpha (TNFα), total antioxidant status (TAS), total oxidant status (TOS), thiobarbituric acid reactive substances (TBARS), interleukin 6 (IL-6), interleukin 10 (IL-10) levels were analyzed. Spinal cord neuronal damage score and apoptotic cell count were also investigated.

RESULTS

I/R injury significantly increases the plasma and spinal cord tissue TNFα, TOS, TBARS, and IL-6 levels and decreases the plasma and spinal cord tissue TAS and IL-10 levels. Tocilizumab treatment significantly reduces the plasma and spinal cord tissue TNFα, TOS, TBARS, IL-6 levels and increases plasma and tissue TAS and IL-10 levels. I/R injury significantly increases spinal cord neuronal damage score and apoptotic cell count. Tocilizumab treatment significantly reduces spinal cord neuronal damage score and apoptotic cell count. Neurologic examination scores at 24, 48, and 72 hours were significantly better in the treatment group when compared with the I/R group.

CONCLUSIONS

This study shows significant neuroprotective effects of tocilizumab on rabbit spinal cord I/R injury.

Computational Analysis Supports IL-17A as a Central Driver of Neutrophil Extracellular Trap-Mediated Injury in Liver Ischemia Reperfusion

Hepatic ischemia reperfusion (I/R) is a clinically relevant model of acute sterile inflammation leading to a reverberating, self-sustaining inflammatory response with resultant necrosis. We hypothesized that computerized dynamic network analysis (DyNA) of 20 inflammatory mediators could help dissect the sequence of post-I/R mediator interactions that induce injury. Although the majority of measured inflammatory mediators become elevated in the first 24 h, we predicted that only a few would be secreted early in the process and serve as organizational centers of downstream intermediator complexity. In support of this hypothesis, DyNA inferred a central organizing role for IL-17A during the first 3 h of reperfusion. After that, DyNA revealed connections among almost all the inflammatory mediators, representing an ongoing cytokine storm. Blocking IL-17A immediately after reperfusion disassembled the inflammatory networks and protected the liver from injury. Disassembly of the networks was not achieved if IL-17A blockage was delayed two or more hours postreperfusion. Network disassembly was accompanied by decrease in neutrophil infiltration and neutrophil extracellular trap (NET) formation. By contrast, administration of recombinant IL-17A increased neutrophil infiltration, NET formation, and liver necrosis. The administration of DNase, a NET inhibitor, significantly reduced hepatic damage despite prior administration of IL-17A, and DNase also disassembled the inflammatory networks. In vitro, IL-17A was a potent promoter of NET formation. Therefore, computational analysis identified IL-17A's early, central organizing role in the rapid evolution of a network of inflammatory mediators that induce neutrophil infiltration and NET formation responsible for hepatic damage after liver I/R.

Proteome variation of the rat liver after static cold storage assayed in an ex vivo model

Cold storage is a common procedure for liver preservation in a transplant setting. However, during cold ischemia, the liver suffers molecular alterations that can affect its performance. Also, deleterious mechanisms set forth in the storage phase are exacerbated during reperfusion. This study aimed to identify liver proteins associated with injury during cold storage and/or normothermic reperfusion using the isolated perfused rat liver model. Livers from male rats were subjected to either (1) cold storage for 24 h, (2) ex vivo normothermic reperfusion for 90 min or (3) cold storage for 24 h followed by ex vivo normothermic reperfusion for 90 min. Then, the livers were homogenized and proteins were extracted. Protein expression between each experimental group and the control (freshly resected livers) was compared by two-dimensional (2D) gel electrophoresis. Protein identification was carried out by matrix-assisted laser desorption/ionization time-of-flight spectrometry (MALDI-TOF/TOF) using MASCOT as the search engine. 23 proteins were detected with significantly altered levels of expression among the different treatments, including molecular chaperones, antioxidant enzymes, and proteins involved in energy metabolism. Some of them have been postulated as biomarkers for liver damage while others had been identified in other organs subjected to ischemia and reperfusion injury. The whole data set will be a useful resource for studying deleterious molecular mechanisms that result in diminished liver function during storage and subsequent reperfusion.

Integrated Proteome and Cytokine Profiles Reveal Ceruloplasmin Eliciting Liver Allograft Tolerance via Antioxidant Cascades

Acute rejection (AR) and spontaneous tolerance may occur after allograft orthotopic liver transplants (OLT) performed in certain combinations of donor and recipient rat strains, yet the underlying molecular cascades involved in these conditions remain poorly understood. Comprehensive analysis with proteomic tools revealed that ceruloplasmin was highly expressed during the tolerant period on day 63 post-OLT (POD 63) compared to the rejected samples on POD 14. Meanwhile, cytokine expression profiles implied that the inflammation was significantly stimulated in the AR subjects. Again, protein carbonylation was dramatically upregulated in the rejected subject within the tolerant group. Knockdown of ceruloplasmin would elicit more severe ROS damage, leading to cell death in the presence of H₂O₂, which induced Nrf2 cascade and the recovery of ceruloplasmin to mediate spontaneous tolerance. In summary, ceruloplasmin may contribute to amending the oxidative stress that eventually causes cell apoptosis and to maintaining the survival of hepatocytes in a drug-free tolerance OLT model.

NLRP3 Inflammasome and IL-33: Novel Players in Sterile Liver Inflammation

In sterile liver inflammation, danger signals are released in response to tissue injury to alert the immune system; e.g., by activation of the NLRP3 inflammasome. Recently, IL-33 has been identified as a novel type of danger signal or “alarmin”, which is released from damaged and necrotic cells. IL-33 is a pleiotropic cytokine that targets a broad range of immune cells and exhibits pro- and anti-inflammatory properties dependent on the disease. This review summarizes the immunomodulatory roles of the NLRP3 inflammasome and IL-33 in sterile liver inflammation and highlights potential therapeutic strategies targeting these pathways in liver disease.

Downregulation of the long noncoding RNA MBNL1-AS1 protects sevoflurane-pretreated mice against ischemia-reperfusion injury by targeting KCNMA1

Total knee arthroplasty (TKA) is the most common and cost-effective treatment for older adults with long-standing osteoarthritis. During TKA, muscle cells suffer from prolonged oxygen deficiency, which leads to altered cell metabolism that reduces the energy demand and maintains cell homeostasis before blood flow is restored. This study focused on the role of the lncRNA muscleblind-like 1 antisense RNA 1 (MBNL1-AS1) in protecting sevoflurane-pretreated mice against ischemia-reperfusion (I/R) injury after TKA, as well as the elucidation of the potential associated mechanism. Identification of differentially expressed lncRNAs was performed using the microarray dataset GSE21164, which was extracted from the GEO database. Target genes of the lncRNA were determined using Multi-Experiment Matrix (MEM), a dual-luciferase reporter gene assay, and KEGG enrichment analyses. The results showed that MBNL1-AS1 was overexpressed in skeletal muscle cells in mice, while KCNMA1, which was enriched in the cGMP-PKG signaling pathway, was negatively regulated by MBNL1-AS1. Furthermore, I/R mice displayed serious inflammatory reactions. Down-regulation of MBNL1-AS1 increased the expression of KCNMA1, PKGII, VASP, VEGF, Bcl-2, Cyclin D1, Cyclin D3, and Cdc 42 but decreased the expression of Bax, cleaved caspase-3, and cleaved PARP. Furthermore, upon MBNL1-AS1 upregulation, the rate of cell apoptosis increased while the rate of cell proliferation decreased. Our data suggested that down-regulated lncRNA MBNL1-AS1 might promote the proliferation and inhibit the apoptosis of skeletal muscle cells by upregulating KCNMA1 expression via activation of the cGMP-PKG signaling pathway, thus protecting sevoflurane-pretreated mice against I/R injury after TKA.

A potential therapeutic target identified by researchers in China could help limit damage to tissues following osteoarthritic knee surgery. A total knee arthroplasty can alleviate symptoms of end-stage osteoarthritis, but the surgery requires use of a tourniquet. This temporarily cuts blood supply to tissues and can trigger severe ischemia-reperfusion (I/R) injury, tissue damage caused by blood flow returning after oxygen deficiency. Shao-Nan Yu and co-workers at the China-Japan Union Hospital of Jilin University, Changchun, demonstrated that lowering expression of a particular RNA molecule following surgery could limit I/R damage. They found that the molecule was over-expressed in mice during I/R injury. This overexpression limited activation of a signalling pathway and an associated protein vital to the chemical balance of cell membranes and healthy muscle cell contraction.

Interaction between anesthetic conditioning and ischemic preconditioning on metabolic function after hepatic ischemia-reperfusion in rabbits

BACKGROUND

Both anesthetic-induced and ischemic preconditioning are protective against hepatic ischemia-reperfusion injury. However, the effects of these preventive methods on the metabolic function remain to be elucidated. We investigated the anesthetic conditioning and ischemic preconditioning on the metabolic function of the rabbit model of hepatic ischemia-reperfusion.

METHODS

After approval by the institutional animal care and use committee, 36 Japanese White rabbits underwent partial hepatic ischemia for 90 min either under sevoflurane or propofol anesthesia. All the rabbits underwent 90 min of hepatic ischemia, and half of the rabbits in each group underwent additional 10-min ischemia and 10-min reperfusion before index ischemia. Hepatic microvascular blood flow was intermittently measured during reperfusion period, and galactose clearance, serum aminotransferase activities, and lactate concentrations were determined 180 min after reperfusion.

RESULTS

Neither anesthetic conditioning with sevoflurane nor ischemic preconditioning altered hepatic microvascular blood flow during reperfusion and serum transaminase activities after reperfusion. However, galactose clearance of reperfused liver was significantly higher under sevoflurane anesthesia than propofol (0.016 ± 0.005/min vs. 0.011 ± 0.004/min). Statistically significant interaction between anesthetic choice and application of ischemic preconditioning suggests that the ischemic preconditioning is selectively protective under propofol anesthesia. Increase of blood lactate concentration was significantly suppressed under sevoflurane anesthesia compared to propofol (1.5 ± 0.8 vs. 3.9 ± 1.4 mmol/l) without any statistically significant interaction with the application of ischemic preconditioning.

CONCLUSION

Sevoflurane attenuated the decrease of galactose clearance and increase of the blood lactate after reperfusion compared to propofol. Application of ischemic preconditioning was significantly protective under propofol anesthesia.

Baicalin attenuates liver hypoxia/reoxygenation injury by inducing autophagy

The aim of the present study was to explore the effect of baicalin on liver hypoxia/reoxygenation (H/R) injury and the possible mechanism involved. A cellular H/R model was established and cells were treated with 50, 100 and 200 µmol/l baicalin. Following reoxygenation for 6 h, cell viability, lactate dehydrogenase (LDH), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase 3 and cleaved caspase 3 were assessed. Furthermore, levels of endoplasmic reticulum stress markers binding of immunoglobulin protein (BIP) and CCAAT/enhancer-binding protein homologous protein (CHOP) and autophagy markers microtubule-associated proteins 1A/1B light chain 3B (LC3) and beclin 1 were measured. To confirm the involvement of autophagy in baicalin-mediated attenuation of H/R injury, the autophagy inhibitor 3-methyladenine (3-MA) was administered. The results revealed that baicalin administration increased cell viability and decreased LDH levels, most notably at a dosage of 100 µmol/l. Baicalin pretreatment also downregulated the expression of caspase 3, cleaved caspase 3 and Bax, while upregulating the expression of Bcl-2. Furthermore, BIP and CHOP were decreased while LC3 and beclin-1 were significantly increased by baicalin pretreatment. Inhibiting autophagy using 3-MA, resulted in a significant decrease in LC3-II, beclin-1 and LDH, as well as increase in the expression of BIP, CHOP, caspase 3, cleaved caspase 3 and Bax. Bcl-2 and cell viability were also decreased. In conclusion, the results of the present study indicate that baicalin exerts a protective effect on liver H/R injury and this may be achieved via the induction of autophagy.

Preventive Effect of Antioxidative Nutrient-Rich Enteral Diet Against Liver Ischemia and Reperfusion Injury

BACKGROUND

Liver ischemia and reperfusion injury (IRI) is a major problem associated with liver surgery. This study is aimed to compare the preventive effect of an antioxidative nutrient-rich enteral diet (Ao diet) with an ordinal enteral diet (control diet) against liver IRI.

METHODS

The Ao diet was an ordinary diet comprising polyphenols (catechin and proanthocyanidin) and enhanced levels of vitamins C and E. Male C57BL/6 mice were fed the Ao or control diet for 7 days before ischemic insult for 60 minutes, followed by reperfusion for 6 hours. The levels of inflammatory cytokines, chemokines, and antioxidant enzymes and oxidative stress were evaluated.

RESULTS

After 7 days of pretreatment with the Ao diet, the serum levels of vitamins C and E in mice were markedly elevated. The levels of serum aspartate aminotransferase and alanine aminotransferase, as well as the scores of liver necrosis caused by ischemia and reperfusion, were significantly lower in the Ao diet group than in the control diet group. The gene expression levels of inflammatory cytokines and chemokines, such as interleukin-6 and CXCL1, were significantly lower in the Ao diet group. In the liver, the levels of antioxidant enzymes superoxide dismutase 1 (SOD1) and SOD2 were significantly higher and the malondialdehyde levels were significantly lower in the Ao diet group. Cell adhesion molecule expression was significantly lower, and neutrophil and macrophage infiltration was less in the Ao diet group.

CONCLUSIONS

Antioxidative nutrient supplementation to an ordinary enteral diet may mitigate liver IRI by causing an antioxidant effect and suppressing inflammation.