Role of Kupffer cells in ischemic injury in alcoholic fatty liver

ER stress promotes mitochondrial calcium overload and activates the ROS/NLRP3 axis to mediate fatty liver ischemic injury

BACKGROUND

Fatty livers are widely accepted as marginal donors for liver transplantation but are more susceptible to liver ischemia and reperfusion (IR) injury. Increased macrophage-related inflammation plays an important role in the aggravation of fatty liver IR injury. Here, we investigate the precise mechanism by which endoplasmic reticulum (ER) stress activates macrophage NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) signaling by regulating mitochondrial calcium overload in fatty liver IR.

METHODS

Control- and high-fat diet-fed mice were subjected to a partial liver IR model. The ER stress, mitochondrial calcium levels, and NLRP3 signaling pathway in macrophages were analyzed.

RESULTS

Liver steatosis exacerbated liver inflammation and IR injury and enhanced NLRP3 activation in macrophages. Myeloid NLRP3 deficiency attenuated intrahepatic inflammation and fatty liver injury following IR. Mechanistically, increased ER stress and mitochondrial calcium overload were observed in macrophages obtained from mouse fatty livers after IR. Suppression of ER stress by tauroursodeoxycholic acid effectively downregulated mitochondrial calcium accumulation and suppressed NLRP3 activation in macrophages, leading to decreased inflammatory IR injury in fatty livers. Moreover, Xestospongin-C-mediated inhibition of mitochondrial calcium influx decreased reactive oxygen species (ROS) expression in macrophages after IR. Scavenging of mitochondrial ROS by mito-TEMPO suppressed macrophage NLRP3 activation and IR injury in fatty livers, indicating that excessive mitochondrial ROS production was responsible for macrophage NLRP3 activation induced by mitochondrial calcium overload. Patients with fatty liver also exhibited upregulated activation of NLRP3 and the ER stress signaling pathway after IR.

CONCLUSIONS

Our findings suggest that ER stress promotes mitochondrial calcium overload to activate ROS/NLRP3 signaling pathways within macrophages during IR-stimulated inflammatory responses associated with fatty livers.

CD47 blockade alleviates acute rejection of allogeneic mouse liver transplantation by reducing ischemia/reperfusion injury

Despite advances in immunosuppressive therapies, acute rejection response is still a serious concern especially in the early phase after liver transplantation. This study aimed to evaluate whether blocking the TSP1-CD47 signaling pathway could attenuate the acute rejection after liver transplantation. An allogeneic mouse orthotopic liver transplantation model (Balb/c→C3H) with prolonged cold ischemic phase was used to induce severe IRI and lethal acute rejection. CD47mAb or isotype matched-control IgG_2a was administered to donor liver during graft perfusion. Recipients were sacrificed at 1d, 3d, 5d and 7d after reperfusion. Blood samples were collected to evaluate serum alanine aminotransferase, total bilirubin, HMGB-1,TNF-α, IL-2 and INF-γ level. Flow cytometric analysis was used to detect the strength of innate and adaptive immune response. Liver tissue was obtained for HE, TUNEL staining and F4/80 immumohistochemical staining. Moreover, we conducted a mixed lymphocyte reaction treated with IgG_2a or CD47mAb. Mice in CD47mAb-treated group demonstrated improved survival and significantly lower increase in Suzuki score, apoptosis index, acute rejection index, serum alanine aminotransferase, total bilirubin, HMGB-1, TNF-α, IL-2, INF-γ level and the degree of Kupffer cells' activation especially in the early phase of acute rejection. In addition, Pearson's correlation analysis confirmed significant correlation between Suzuki score/ALT and acute rejection index. The in vitro inhibition assay showed that CD47 blockade couldn't directly inhibit recipient lymphocyte proliferation. Based on the evidence that TSP1-CD47 signaling blockade with CD47mAb could alleviate acute rejection by reducing the extent of IRI after liver transplantation indirectly, this study provided a basis for new interventions and management methods to support better transplant outcomes.

Coenzyme Q10 protects hepatocytes from ischemia reperfusion-induced apoptosis and oxidative stress via regulation of Bax/Bcl-2/PUMA and Nrf-2/FOXO-3/Sirt-1 signaling pathways

Coenzyme Q₁₀ (CoQ₁₀) is a component of the mitochondrial electron transport chain and regarded as a strong anti-oxidant agent. In this study, we focused on the mechanistic insights involved in the hepato-protective effects of CoQ₁₀ against hepatic ischemia reperfusion (IR) injury. Our results revealed that CoQ₁₀ significantly improved hepatic dysfunctions and oxidative stress caused by IR injury. Interestingly, as compared to IR subjected rat, CoQ₁₀ inhibited apoptosis by marked down-regulation of both Bax and PUMA genes while the level of Bcl-2 gene was significantly increased. Moreover, CoQ₁₀ up-regulated PI3K, Akt and mTOR protein expressions while it inhibited the expression of both GSK-3β and β-catenin. Additionally, CoQ₁₀ restored oxidant/antioxidant balance via marked activated Nrf-2 protein as well as up-regulation of both Sirt-1 and FOXO-3 genes. Moreover, CoQ₁₀ strongly inhibited inflammatory response through down-regulation of NF-κB-p65 and decrease both JAK1 and STAT-3 protein expressions with a subsequent modulating circulating inflammatory cytokines. Furthermore, histopathological analysis showed that CoQ₁₀ remarkably ameliorated the histopathological damage induced by IR injury. Taken together, our results suggested and proved that CoQ₁₀ provided a hepato-protection against hepatic IR injury via inhibition of apoptosis, oxidative stress, inflammation and their closed related pathways.

Histopathological changes and onset of severe hepatic steatosis in rats fed a choline-free diet

Hepatic steatosis significantly increases morbidity and mortality associated with major liver surgery. Several rodent models of hepatic steatosis have been previously reported, which aimed to investigate the effect of various pharmaceutical agents and interventional procedures on the pathophysiology of steatotic liver. The aim of the present study was to investigate the time frame of severe hepatic steatosis in rats after they were fed a choline-free diet and any associated histopathological changes. The duration of feeding with a choline-free diet required to develop severe hepatic steatosis was investigated in Wistar rats. The severity of hepatic steatosis in liver specimens was evaluated at 8, 10, 12 and 14 weeks following the onset of the choline-free diet. Comparisons were made with rats receiving standardized laboratory food. Feeding rats for 12–13 weeks with a choline-free diet led to 66% fatty liver infiltration, which exceeded 68% after 14 weeks. Prior to 8 weeks, the fatty infiltration reached 43%, with a gradual increase revealing a stronger rate from 8–12 weeks and a gradual decline after 14 weeks. At 12–13 weeks the fatty infiltration was considered representative of severe hepatic steatosis. Macrovesicular fatty infiltration revealed a significant increase at a steady rate between 8 and 14 weeks, with evidence of the onset of lobular inflammation and steatohepatitis after 14 weeks of feeding with the choline-free diet. Microvesicular fatty infiltration demonstrated a lower growth rate between 8 and 12 weeks while maintaining a steady rate between 12 and 14 weeks. Mixed fatty infiltration maintained its steady rate of hepatic parenchyma from 8.8–9.5%. Rats fed with the standard laboratory diet did not demonstrate fatty infiltration >4.5%, so they did not develop hepatic steatosis. Developing an ideal model of hepatic steatosis is a particular challenge. The findings of the present study indicate that severe hepatic steatosis in rodents may lead to the development of steatohepatitis after feeding with a choline-free diet for at least 14 weeks. This model is of particular interest in experimental liver surgery and associated surgical maneuvers, and is easily reproducible.

Ketamine ameliorates ischemia-reperfusion injury after liver autotransplantation by suppressing activation of Kupffer cells in rats

This study aimed to investigate the protective effects of ketamine against hepatic ischemia-reperfusion (I/R) injury by suppressing activation of Kupffer cells (KCs) in rat liver autotransplantation. Male Sprague-Dawley rats were randomized into 3 groups (n = 10 each). Group I, the sham group, received saline. Group II received saline and underwent orthotopic liver autotransplantation (OLAT). Group III received 10 mg/kg ketamine and underwent OLAT. Blood samples were obtained at 3, 6, 12, and 24 h after I/R, and following ALT, AST, LDH, IL-6, TNF-α, IL-1β, and IL-10 in serum were detected. Model rats were sacrificed at the indicated time points and the graft liver tissues were evaluated histologically. KCs were isolated from rat liver tissues, and inflammatory products and proteins of NF-κB signaling pathway were detected using quantitative RT-PCR and Western blotting. Our results showed that ketamine significantly decreased ALT, AST, LDH, IL-6, TNF-α, and IL-1β levels and increased IL-10 level. Furthermore, ketamine alleviated the histopathology changes, by less KC infiltration and lower hepatocyte apoptosis. Moreover, activity of NF-κB signaling pathway in KCs was suppressed. In addition, production of pro- and anti-inflammatory factors is consistent with the results in tissues. Ketamine ameliorated I/R injury after liver transplantation by suppressing activation of KCs in rats.

Cytochrome P450 1A1 and 1B1 promoter CpG island methylation regulates rat liver injury induced by isoniazid

DNA methylation is an important component of epigenetics that is involved in the occurrence and development of a variety of diseases. The present study aimed to clarify the relationship between cytochrome P450 (CYP)1A1 and CYP1B1 promoter CpG island methylation and isoniazid-induced liver injury in rats, and to explore the possible mechanism, rats were given an intragastric dose of isoniazid (55 mg·kg⁻¹·d⁻¹). High performance liquid chromatography was used to analyze the DNA methylation level of the whole genome in liver tissue. Methylation-specific polymerase chain reaction (PCR) was used to detect the methylation level of CpG islands in the promoter region of CYP1A1 and CYP1B1. Reverse transcription-quantitative PCR was used to determine the mRNA expression levels of CYP1A1, CYP1B1, toll-like receptor 4 (TLR4), extracellular signal-regulated kinase (ERK) 2, peroxisome proliferator-activated receptor (PPAR) -γ, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. The expression levels of CYP1A1 and CYP1B1 proteins were measured by ELISA, and malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were analyzed by colorimetric method. Liver tissue pathology, an indicator of liver function, indicated rat liver injury at 10 days following isoniazid treatment. Whole-genome methylation levels were gradually reduced, and methylation at day 7 post-treatment was significantly lower than the control group. CYP1A1 and CYP1B1 promoter CpG island methylation level was significantly increased at 3 days post-treatment. CYP1A1 and CYP1B1 mRNA expression levels were significantly reduced from day 7 and 10, respectively. These results suggested that CpG island hypermethylation of the CYP1A1 and CYP1B1 promoters regulate the low expression of genes involved in the occurrence of isoniazid-induced liver injury. With the alterations of CYP1A1 and CYP1B1 expression, the mRNA expression levels of TLR4, ERK, MDA, IL-6 and TNF-α were upregulated, and the expression of SOD and PPAR-γ were downregulated. These data demonstrated that alterations in methylation patterns may involve changes in the TLR4-ERK signaling pathway and PPAR-γ, which may alter the expression of MDA, SOD, IL-6 and TNF-α, leading to liver injury.

The natural product fucoidan ameliorates hepatic ischemia-reperfusion injury in mice

Fucoidan is a sulfated polysaccharide based predominantly on l-fucose, and has several biologic functions. Reactive oxygen species-mediated apoptosis and autophagy and release of related inflammatory factors have important roles in hepatic ischemia-reperfusion injury (IR). Here, the effect of fucoidan on hepatic IR was investigated. Mice were randomized into sham, IR, and fucoidan (20, 40mg/kg for 14days) groups. Samples were collected to assess biochemical indicators, hepatocyte damage and levels of proteins related to signaling pathways at different time points. Fucoidan had no effect on normal liver tissue, but inhibited the increases in alanine aminotransferase, aspartate transaminase, inflammatory factors, and the hepatocyte damage caused by IR. Also, apoptosis and autophagy via the activated JAK2/STAT1 pathway were attenuated by fucoidan to protect against hepatic injury. In conclusion, fucoidan ameliorates hepatic IR injury in mice via JAK2/STAT1-mediated apoptosis and autophagy. Inhibition of this pathway may be associated with reduced release of related inflammatory cytokines, especially interferon-γ.

Intermittent Ischemic Preconditioning Protects Against Hepatic Ischemia-Reperfusion Injury and Extensive Hepatectomy in Steatotic Rat Liver

BACKGROUND

Hepatic steatosis causes severe liver damage and has deleterious effects when associated with ischemia-reperfusion mechanisms. Ischemic preconditioning (IPC) protects lean liver against prolonged ischemia by improving micro-circulation and reducing lipid peroxidation. We investigated the effect of intermittent IPC on liver ischemia-reperfusion injury (IRI) and extensive hepatectomy in severe hepatic steatosis.

METHODS

Severe hepatic steatosis was performed by 12-14 weeks of choline-free diet in 108 Wistar rats. We induced 30-minute ischemia-reperfusion manipulations and extensive hepatectomy with or without prior IPC in steatotic livers and after 6 and 24 hours of reperfusion blood transaminases, and IL6, TNFα, NO and Lactate in blood and liver tissue were measured.

RESULTS

Steatotic rats subjected to hepatic ischemia-reperfusion alone after extensive hepatectomy, showed severe liver damage with significantly increased values of AST, ALT, TNFα and Lactate and significantly reduced IL6 and NO, while no one rat survived for more than 29 hours. On the contrary, steatotic rats subjected to intermittent IPC, 24 hours before ischemia-reperfusion, presented increased 30-day survival (67%), lower values of AST, ALT, TNFα and Lactate, and increased IL6 and NO levels. Simple and intermittent IPC manipulations, 1 hour before the IRI and extended hepatectomy, did not prolong survival more than 57 and 98 hours, respectively. Simple IPC, 24 hours before IRI and extended hepatectomy had the lowest possible survival (16.7%).

CONCLUSIONS

Hepatic steatosis and IRI after major liver surgery largely affect morbidity and mortality. Intermittent IPC, 24 hours before IRI and extensive hepatectomy, presents higher 30-day survival and improved liver function parameters.

Nobiletin ameliorates ischemia-reperfusion injury by suppressing the function of Kupffer cells after liver transplantation in rats

This study aims to explore the protective effects of nobiletin against hepatic ischemia-reperfusion (IR) injury after liver transplantation. Kupffer cells (KCs) were activated and co-cultured with different concentration of nobiletin for 24h in vitro, inflammatory products and activity of TLR4/NF-κB signaling pathway were detected. Sprague-Dawley rats were selected and underwent orthotopic liver transplantation. Donors were injected intravenously with nobiletin (50mg/kg) or saline solution, once a day for 1 week before the surgery. Recipients were randomly paired and sacrificed at the indicated time points (3, 6, and 24h after the surgery), the graft liver tissues and blood samples were collected for analysis. Hepatic function, inflammatory mediators, apoptosis of hepatocytes, histological changes, KCs and CD4+ T-lymphocyte infiltration were assessed. Results showed nobiletin dose-dependently suppressed the expression of inflammatory mediators and the activity of TLR4/NF-κB signaling pathway in activated KCs. Furthermore, nobiletin alleviated liver damage induced by IR in vivo, significantly decreased the serum levels of alanine aminotransferase, aspartate transaminase, inflammatory cytokines and alleviated the histopathology changes. Moreover, liver in the nobiletin treated group exhibited less KCs and CD4+ lymphocyte infiltration and lower hepatocyte apoptosis after operation. In addition, activity of TLR4/NF-κB signaling pathway in KCs was also suppressed, consistent with the results in vitro. Collectively, Nobiletin can ameliorate IR injury after liver transplantation and may be a promising new strategy to protect against liver IR injury.

Ultra-sensitive diagnosis of orthotopic patient derived hepatocellular carcinoma by Fe@graphene nanoparticles in MRI

mPEG-DSPE modified Fe/graphene nanoparticles showed low cytotoxicity and high magnetic performance, providing super MRI diagnostic ability for cancer detection.

Astaxanthin Pretreatment Attenuates Hepatic Ischemia Reperfusion-Induced Apoptosis and Autophagy via the ROS/MAPK Pathway in Mice

Background: Hepatic ischemia reperfusion (IR) is an important issue in complex liver resection and liver transplantation. The aim of the present study was to determine the protective effect of astaxanthin (ASX), an antioxidant, on hepatic IR injury via the reactive oxygen species/mitogen-activated protein kinase (ROS/MAPK) pathway. Methods: Mice were randomized into a sham, IR, ASX or IR + ASX group. The mice received ASX at different doses (30 mg/kg or 60 mg/kg) for 14 days. Serum and tissue samples at 2 h, 8 h and 24 h after abdominal surgery were collected to assess alanine aminotransferase (ALT), aspartate aminotransferase (AST), inflammation factors, ROS, and key proteins in the MAPK family. Results: ASX reduced the release of ROS and cytokines leading to inhibition of apoptosis and autophagy via down-regulation of the activated phosphorylation of related proteins in the MAPK family, such as P38 MAPK, JNK and ERK in this model of hepatic IR injury. Conclusion: Apoptosis and autophagy caused by hepatic IR injury were inhibited by ASX following a reduction in the release of ROS and inflammatory cytokines, and the relationship between the two may be associated with the inactivation of the MAPK family.

Role of Kupffer cells in bacterial infectious diseases

Kupffer cells (KCs) are also known as liver inherent macrophages, which account for the largest part of human tissue macrophages and participate in the pathogenesis of various liver diseases. In vitro study using primary culture is a valuable tool for the exploration of specific immunological functions of KCs. Obtaining KCs with high purity and activity is the basis for research. A large number of phagocytosable particles and soluble substances can activate KCs by binding to specific receptors on the membrane. The most important molecule that activates KCs is lipopolysaccharide (LPS). A tiny quantity of LPS will drive a Toll-like receptor 4 (TLR4) -dependent proinflammatory response that alerts the host to the presence of infection. Higher quantities of LPS, which reach the cytoplasm, will trigger inflammasome activation, interleukin-1 beta (IL-1β) production and, ultimately, cell death. KCs play an important role in sepsis, endotoxin tolerance and acute pancreatitis. In this review, we describe the role of KCs in these diseases and the underlying molecular mechanisms.