Lipopolysaccharide preconditioning protects hepatocytes from ischemia/reperfusion injury (IRI) through inhibiting ATF4-CHOP pathway in mice. PLoS One. 2013;8:e65568. [PMID: 23750267 PMCID: PMC3672158 DOI: 10.1371/journal.pone.0065568]

CTGF regulated by ATF6 inhibits vascular endothelial inflammation and reduces hepatic ischemia-reperfusion injury

Vascular endothelial inflammation is crucial in hepatic ischemia-reperfusion injury (IRI). Our previous research has shown that connective tissue growth factor (CTGF), secreted by endothelial cells, protects against acute liver injury, but its upstream mechanism is unclear. We aimed to clarify the protective role of CTGF in endothelial cell inflammation during IRI and reveal the regulation between endoplasmic reticulum stress-induced activating transcription factor 6 (ATF6) and CTGF. Hypoxia/reoxygenation in endothelial cells, hepatic IRI in mice and clinical specimens were used to examine the relationships between CTGF and inflammatory factors and determine how ATF6 regulates CTGF and reduces damage. We found that activating ATF6 promoted CTGF expression and reduced liver damage in hepatic IRI. In vitro, activated ATF6 upregulated CTGF and downregulated inflammation, while ATF6 inhibition had the opposite effect. Dual-luciferase assays and chromatin immunoprecipitation confirmed that activated ATF6 binds to the CTGF promoter, enhancing its expression. Activated ATF6 increases CTGF and reduces extracellular regulated protein kinase 1/2 (ERK1/2) phosphorylation, decreasing inflammatory factors. Conversely, inhibiting ATF6 decreases CTGF and increases the phosphorylation of ERK1/2, increasing inflammatory factor levels. ERK1/2 inhibition reverses this effect. Clinical samples have shown that CTGF increases after IRI, inversely correlating with inflammatory cytokines. Therefore, ATF6 activation during liver IRI enhances CTGF expression and reduces endothelial inflammation via ERK1/2 inhibition, providing a novel target for diagnosing and treating liver IRI.

XBP1 Facilitating NF-κB-p65 Nuclear Translocation Promotes Macrophage-Originated Sterile Inflammation Via Regulating MT2 Transcription in the Ischemia/Reperfusion Liver

BACKGROUND & AIMS

XBP1, most conserved transcription factor of endoplasmic reticulum stress, plays important roles in physiological and pathologic settings and has profound effects on disease progression and prognosis, so it is necessary to investigate XBP1 in macrophage-originated sterile inflammation during liver ischemia/reperfusion injury (IRI). Macrophage XBP1 expression and liver injury are analyzed in patients undergoing ischemia-related hepatectomy.

METHODS

A myeloid-specific male XBP1-knockout (XBP1M-KO) strain is created for function and mechanism of XBP1 on macrophage-derived sterile inflammation in murine liver IRI with in vitro parallel research. Macrophages cocultured with hypoxia-treated hepatocytes are applied to investigate impact of XBP1 in vitro, with analysis of RNA sequencing and databases.

RESULTS

Clinically, macrophage XBP1 expression significantly increases in ischemic liver tissues and positively correlates with liver injury after hepatectomy. Less hepatocellular damage is presented in XBP1M-KO mice than in XBP1-proficient (XBP1FL/FL) control animals. In vitro, XBP1 deficiency inhibits sterile inflammation and migration in macrophages cocultured with hypoxia-treated hepatocytes. Analysis of RNA sequencing and databases determines Metallothionein 2 (MT2) as XBP1 target gene, negatively regulated by binding with its promoter. XBP1 deficiency increases MT2 and IKBα expression, but inhibits nuclear factor-κB-p65 phosphorylation, markedly neutralizing XBP1M-KO-related benefits by promoting sterile inflammation during liver IRI.

CONCLUSIONS

XBP1 promotes macrophage-originated sterile inflammation, increases liver IRI by binding to MT2 promoter, and regulates MT2/nuclear factor-κB pathway, potentially therapeutic for clinical liver IRI.

Mitochondrial unfolded protein response in ischemia-reperfusion injury

Mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that activates the transcriptional program of mitochondrial chaperone proteins and proteases to keep protein homeostasis in mitochondria. Ischemia-reperfusion injury results in multiple severe clinical issues linked to high morbidity and mortality in various disorders. The pathophysiology and pathogenesis of ischemia-reperfusion injury are complex and multifactorial. Emerging evidence showed the roles of UPRmt signaling in ischemia-reperfusion injury. Herein, we discuss the regulatory mechanisms underlying UPRmt signaling in C. elegans and mammals. Furthermore, we review the recent studies into the roles and mechanisms of UPRmt signaling in ischemia-reperfusion injury of the heart, brain, kidney, and liver. Further research of UPRmt signaling will potentially develop novel therapeutic strategies against ischemia-reperfusion injury.

Resveratrol promotes liver cell survival in mice liver-induced ischemia-reperfusion through unfolded protein response: a possible approach in liver transplantation

Background

Ischemia-reperfusion (I/R) of the liver is a multifactorial condition that happens during transplantation and surgery. The deleterious effects of I/R result from the acute production of reactive oxygen species (ROS), which can trigger immediate tissue damage and induce a series of destructive cellular responses, including apoptosis organ failure and inflammation. The production of ROS in the I/R process can damage the antioxidant system and cause liver damage. Resveratrol has been shown to have antioxidant properties in several investigations. Here, we address the therapeutic effect of resveratrol on I/R-induced liver injury by focusing on unfolded protein response (UPR) signaling pathway.

Methods

Five minutes before reperfusion, resveratrol was injected into the tail vein of mice. They were ischemic for 1 h and then re-perfused for 3 h before being slaughtered (I/R). The activity of liver enzymes and the expression levels of genes involved in the unfolded protein response pathway were used to measure the hepatic damage.

Results

Our results revealed that the low dose of resveratrol (0.02 and 0.2 mg/kg) post-ischemic treatment significantly reduced the ALT and AST levels. In addition, compared with the control group, the expression of UPR pathway genes GRP78, PERK, IRE1α, CHOP, and XBP1 was significantly reduced in the resveratrol group. In the mice that received lower doses of resveratrol (0.02 and 0.2 mg/kg), the histopathological changes induced by I/R were significantly improved; however, the highest dose (2 mg/kg) of resveratrol could not significantly protect and solve the I/R damage.

Conclusion

The findings of this study suggest that hepatic ischemia occurs after liver transplantation and that receiving low-dose resveratrol treatment before reperfusion may promote graft survival through inhibition of UPR arms, especially PERK and IRE1α.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-022-00611-4.

Hyperglycemia-triggered ATF6-CHOP pathway aggravates acute inflammatory liver injury by β-catenin signaling

Although hyperglycemia has been documented as an unfavorable element that can further induce liver ischemia–reperfusion injury (IRI), the related molecular mechanisms remain to be clearly elaborated. This study investigated the effective manner of endoplasmic reticulum (ER) stress signaling in hyperglycemia-exacerbated liver IRI. Here we demonstrated that in the liver tissues and Kupffer cells (KCs) of DM patients and STZ-induced hyperglycemic mice, the ER stress-ATF6-CHOP signaling pathway is activated. TLR4-mediated pro-inflammatory activation was greatly attenuated by the addition of 4-phenylbutyrate (PBA), one common ER stress inhibitor. The liver IRI in hyperglycemic mice was also significantly reduced after PBA treatment. In addition, deficiency of CHOP (CHOP^−/−) obviously alleviates the hepatic IRI, and pro-inflammatory effects deteriorated by hyperglycemia. In hyperglycemic mice, β-catenin expression was suppressed while the ATF6-CHOP signal was activated. In the liver tissues of PBA-treated or CHOP^−/− hyperglycemic mice, the expression of β-catenin was restored. Furthermore, CHOP deficiency can induce protection against hyperglycemia-related liver IRI, which was disrupted by the knockdown of β-catenin will cause this protection to disappear. High glucose (HG) treatment stimulated ATF6-CHOP signaling, reduced cellular β-catenin accumulation, and promoted the TLR4-related inflammation of BMDMs. But the above effects were partially rescued in BMDMs with CHOP deficiency or by PBA treatment. In BMDMs cultured in HG conditions, the anti-inflammatory functions of CHOP^−/− were destroyed by the knockdown of β-catenin. Finally, chimeric mice carrying WT or CHOP^−/− BMDMs by bone marrow transplantation were adopted to verify the above conclusion. The current study suggested that hyperglycemia could trigger ER stress-ATF6-CHOP axis, inhibit β-catenin activation, accelerate inflammation, and deteriorate liver IRI, thus providing the treatment potential for management of sterile liver inflammation in DM patients.

Toll-Like Receptor 4 Activation Prevents Rat Cardiac Fibroblast Death Induced by Simulated Ischemia/Reperfusion

Death of cardiac fibroblasts (CFs) by ischemia/reperfusion (I/R) has major implications for cardiac wound healing. In in vivo models of myocardial infarction, toll-like receptor 4 (TLR4) activation has been reported as a cardioprotector; however, it remains unknown whether TLR4 activation can prevent CF death triggered by simulated I/R (sI/R). In this study, we analyzed TLR4 activation in neonate CFs exposed to an in vitro model of sI/R and explored the participation of the pro-survival kinases Akt and ERK1/2. Simulated ischemia was performed in a free oxygen chamber in an ischemic medium, whereas reperfusion was carried out in normal culture conditions. Cell viability was analyzed by trypan blue exclusion and the MTT assay. Necrotic and apoptotic cell populations were evaluated by flow cytometry. Protein levels of phosphorylated forms of Akt and ERK1/2 were analyzed by Western blot. We showed that sI/R triggers CF death by necrosis and apoptosis. In CFs exposed only to simulated ischemia or only to sI/R, blockade of the TLR4 with TAK-242 further reduced cell viability and the activation of Akt and ERK1/2. Preconditioning with lipopolysaccharide (LPS) or treatment with LPS in ischemia or reperfusion was not protective. However, LPS incubation during both ischemia and reperfusion periods prevented CF viability loss induced by sI/R. Furthermore, LPS treatment reduced the sub-G1 population, but not necrosis of CFs exposed to sI/R. On the other hand, the protective effects exhibited by LPS were abolished when TLR4 was blocked and Akt and ERK1/2 were inhibited. In conclusion, our results suggest that TLR4 activation protects CFs from apoptosis induced by sI/R through the activation of Akt and ERK1/2 signaling pathways.

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

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

Progress in research on the roles of TGR5 receptor in liver diseases

TGR5 (G protein-coupled bile acid receptor 1, GPBAR-1) is a G protein-coupled receptor with seven transmembrane domains and is widely distributed in various organs and tissues. As an important bile acid receptor, TGR5 can be activated by primary and secondary bile acids. Increased expression of TGR5 is a risk factor for polycystic liver disease and hepatobiliary cancer. However, there is evidence that the anti-inflammatory effect of the TGR5 receptor and its regulatory effect on hydrophobic bile acid confer protective effects against most liver diseases. Recent studies have shown that TGR5 receptor activation can alleviate the development of diabetic liver fibrosis, regulate the differentiation of natural killer T cells into NKT10 cells, increase the secretion of anti-inflammatory factors, inhibit the invasion of hepatitis B virus, promote white adipose tissue browning, improve arterial vascular dynamics, maintain tight junctions between bile duct cells, and protect against apoptosis. In portal hypertension, TGR5 receptor activation can inhibit the contraction of hepatic stellate cells and improve intrahepatic microcirculation. In addition, the discovery of the regulatory relationship between the TGR5 receptor and miRNA-26a provides a new direction for further studies of the molecular mechanism underlying the effects of TGR5. In this review, we describe recent findings linking TGR5 to various liver diseases, with a focus on the mechanisms underlying its effects and potential therapeutic implications.

TGR5 Attenuated Liver Ischemia-Reperfusion Injury by Activating the Keap1-Nrf2 Signaling Pathway in Mice

Hepatic ischemia/reperfusion injury (IRI) still remains an unavoidable problem in hepatectomy. The inflammatory response plays an important role in its pathogenesis. The plasma membrane-bound G protein-coupled bile acid receptor (TGR5), as one of G protein-coupled receptor (GPCR) families, has been proved to serve a protective role in several liver diseases. However, the exact function of TGR5 in modulating IRI remains obscure. We injected wild mice with a small interfering RNA of TGR5 (si-TGR5) or TGR5 agonist (INT-777) and established liver partial warm ischemia/reperfusion model. The results showed that knockdown of TGR5 significantly aggravated hepatic tissue injury, but treatment with INT-777 could reverse it, as evidenced by serum ALT and AST tests, liver histological injury, cytokines expressions, liver immunohistochemical analysis, and TUNEL staining. The apoptosis-associated proteins were evaluated after reperfusion. Moreover, we used primary bone marrow-derived macrophages (BMDMs) to establish hypoxia/reoxygenation (H/R) model to verify the anti-inflammation effect of TGR5. In in vivo experiments, we used TGR5-siRNA and TGR5 agonist (INT-777) to determine that TGR5 significantly attenuated liver damage after IRI through activating the Keap1-Nrf2 pathway. In addition, we found that overexpression of INT-777-activated TGR5 could reduce oxidative stress and inflammatory response in H/R-induced BMDMs through regulation of Keap1-Nef2 pathway during in vitro experiment. Importantly, these results were completely reversed in si-TGR5 BMDMs. In conclusion, the results indicated that TGR5 could effectively alleviated inflammation response via accelerating the activation of Keap1-Nrf2 signaling pathway during hepatic IRI, which may be meaningful in reducing related inflammatory molecules and adjusting inherent immunity.

Overexpression of TGR5 alleviates myocardial ischemia/reperfusion injury via AKT/GSK-3β mediated inflammation and mitochondrial pathway

Ischemia/reperfusion (I/R) injury reduces cell proliferation, triggers inflammation, promotes cell apoptosis and necrosis, which are the leading reasons of morbidity and mortality in patients with cardiac disease. TGR5 is shown to express in hearts, but its functional role in I/R-induced myocardial injury is unclear. In the present study, we aimed to explore the underlying molecular mechanism of TGR5 in hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury in vitro. The results showed that TGR5 was significantly up-regulated in H9C2 (rat cardiomyocyte cells) and human cardiomyocytes (HCMs) after H/R. Overexpression of TGR5 significantly improved cell proliferation, alleviated apoptosis rate, the activities of caspase-3, cleaved caspases-3 and Bax protein expression levels, and increased Bcl-2 level. Overexpression of TGR5 significantly up-regulated ROS generation, stabilized the mitochondrial membrane potential (MMP), and reduced the concentration of intracellular Ca²⁺ as well as cytosolic translocation of mitochondrial cytochrome c (cyto-c). Meanwhile, overexpressed TGR5 also enhanced the mRNA and protein levels of interleukin (IL)-10, and decreased the mRNA and protein levels of IL-6 and tumor necrosis factor α (TNF-α). The shTGR5+H/R group followed opposite trends. In addition, overexpressed TGR5 induced an increase in the levels of p-AKT and p-GSK-3β. The protective effects of TGR5 were partially reversed by AKT inhibitor MK-2206. Taken together, these results suggest that TGR5 attenuates I/R-induced mitochondrial dysfunction and cell apoptosis as well as inflammation, and these protections may through AKT/GSK-3β pathway.

Mitochondrial Complex I Is an Essential Player in LPS-Induced Preconditioning in Differentiated PC12 Cells

Preconditioning (PC) as a protective strategy against noxious insults can decline cell death and apoptosis. It has been approved that mitochondria play a key role in PC mechanism. The critical role of complex I (CI) in oxidative phosphorylation machinery and intracellular ROS production, particularly in the brain, accentuates its possible role in PC-induced neuroprotection. Here, differentiated PC12 cells were preconditioned with ultra-low dose LPS (ULD, 3 μg/mL) prior to exposure to high concentration of LPS (HD, 750 μg/mL). Our results showed that HD LPS treatment reduces cell viability and CI activity, and intensifies expression of cleaved caspase 3 compared to the control group. Intriguingly, PC induction resulted in enhancement of cell viability and CI activity and reduction of caspase3 cleavage compared to HD LPS group. In order to explore the role of CI in PC, we combined the ULD LPS with rotenone, a CI inhibitor. Following rotenone administration, cell viability significantly reduced while caspase3 cleavage increased compared to PC induction group. Taken together, cell survival and reduction of apoptosis followed by PC can be at least partially attributed to the preservation of mitochondrial CI function.

Role of interleukin-6 in inhibiting hepatic autophagy markers in exercised mice

BACKGROUND

Based on the crosstalk of inflammation with apoptosis, autophagy, and endoplasmic reticulum (ER) stress, the main objective of this study was to explore the role of interleukin-6 (IL-6) on genes and proteins related to these phenomena in the livers of mice submitted to acute exhaustive exercise.

METHODS

Reverse transcription-quantitative polymerase chain reaction and immunoblotting technique were used to evaluate the livers of wild-type (WT) and IL-6 knockout (KO) mice at baseline (BL) and 3 h after the acute exhaustive physical exercise (EE).

RESULTS

Compared to the WT at baseline, the IL-6 KO had lower exhaustion velocity, mRNA levels of Mtor, Ulk1, Map1lc3b, and Mapk14, and protein contents of ATG5 and p-p70S6K/p70S6K. For the WT group, the EE decreased glycemia, mRNA levels of Casp3, Mtor, Ulk1, Foxo1a, Mapk14, and Ppargc1a, and protein contents of ATG5 and p-p70S6K/p70S6K, but increased mRNA levels of Sqstm1. For the IL-6 KO group, the EE decreased glycemia, mRNA levels of Casp3 and Foxo1a, and protein contents of pAkt/Akt and Mature/Pro IL-1beta, but increased mRNA levels of Sqstm1, and protein contents of p-AMPK/AMPK.

CONCLUSION

The inhibition of the hepatic autophagy markers induced by the acute EE was attenuated in IL-6 KO mice, highlighting a new function of this cytokine.

Tanshinone IIA ameliorates cognitive deficits by inhibiting endoplasmic reticulum stress-induced apoptosis in APP/PS1 transgenic mice

Our previous data indicated that tanshinone IIA (tan IIA) improves learning and memory in a mouse model of Alzheimer's disease (AD) induced by streptozotocin via restoring cholinergic function, attenuating oxidative stress and blocking p38 MAPK signal pathway activation. This study aims to estimate whether tan IIA inhibits endoplasmic reticulum (ER) stress-induced apoptosis to prevent cognitive decline in APP/PS1 transgenic mice. Tan IIA (10 mg/kg and 30 mg/kg) was intraperitoneally administered to the six-month-old APP/PS1 mice for 30 consecutive days. β-amyloid (Aβ) plaques were measured by immunohistochemisty and Thioflavin S staining, apoptotic cells were observed by TUNEL, ER stress markers and apoptosis signaling proteins were investigated by western blotting and RT-PCR. Our results showed that tan IIA significantly ameliorates cognitive deficits and improves spatial learning ability of APP/PS1 mice in the nest-building test, novel object recognition test and Morris water maze test. Furthermore, tan IIA significantly reduced the deposition of Aβ plaques and neuronal apoptosis, and markedly prevented abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), inositol-requiring enzyme 1α (IRE1α), activating transcription factor 6 (ATF6), as well as suppressed the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways in the parietal cortex and hippocampus. Moreover, tan IIA induced an up-regulation of the Bcl-2/Bax ratio and down-regulation of caspase-3 protein activity. Taken together, the above findings indicated that tan IIA improves learning and memory through attenuating Aβ plaques deposition and inhibiting ER stress-induced apoptosis. These results suggested that tan IIA might become a promising therapeutic candidate drug against AD.

Acetyl-3-Aminoethyl Salicylate Ameliorates Hepatic Ischemia/Reperfusion Injury and Liver Graft Survival Through a High-Mobility Group Box 1/Toll-Like Receptor 4-Dependent Mechanism

In liver transplant cases, severe hepatic ischemia/reperfusion injury (HIRI) is a strong predictor of adverse liver graft and overall outcomes. During HIRI, high-mobility group box 1 (HMGB1) promotes hepatocellular death and proinflammatory cytokine secretion by toll-like receptor 4 (TLR4). Because salicylates inhibit HMGB1/TLR4 interaction, we hypothesized that salicylates may ameliorate HIRI-induced liver damage by inhibiting HMGB1/TLR4 axis activation. Using a murine model of HIRI, we found that the salicylate acetyl-3-aminoethyl salicylic acid (ac3AESA) reduced serum alanine aminotransferase and aspartate aminotransferase as well as Suzuki scores and apoptotic cell counts after HIRI. Ac3AESA also down-regulated hepatocellular HMGB1 and TLR4 expression, phosphorylated inhibitor of κBα, extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, cleaved caspase 3, and cleaved caspase 1 levels after HIRI. Ac3AESA reduced liver Kupffer cell transcription of proinflammatory mediators tumor necrosis factor α (TNF-α), interleukin (IL) 6, IL1β, chemokine (C-X-C motif) ligand (CXCL) 1, CXCL2, and CXCL8 after HIRI. Ac3AESA also dose-dependently reduced in vitro release of Kupffer cell TNF-α. Employing a murine orthotopic liver transplantation model, we found daily ac3AESA administration up to day 10 after transplant improved liver graft survival, suppressed allograft damage, and down-regulated HMGB1/TLR4 signaling. These benefits to survival and allograft health were maintained for cold ischemia times of 12 and 18 hours. Notably, TLR4 knockout eliminated all foregoing ac3AESA-induced effects. In conclusion, ac3AESA partially rescues the negative effects of HIRI and prolongs liver graft survival in a TLR4-dependent manner.

Curcumin mitigates axonal injury and neuronal cell apoptosis through the PERK/Nrf2 signaling pathway following diffuse axonal injury

Diffuse axonal injury (DAI) accounts for more than 50% of all traumatic brain injury. In response to the mechanical damage associated with DAI, the abnormal proteins produced in the neurons and axons, namely, β-APP and p-tau, induce endoplasmic reticulum (ER) stress. Curcumin, a major component extracted from the rhizome of Curcuma longa, has shown potent anti-inflammatory, antioxidant, anti-infection, and antitumor activity in previous studies. Moreover, curcumin is an activator of nuclear factor-erythroid 2-related factor 2 (Nrf2) and promotes its nuclear translocation. In this study, we evaluated the therapeutic potential of curcumin for the treatment of DAI and investigated the mechanisms underlying the protective effects of curcumin against neural cell death and axonal injury after DAI. Rats subjected to a model of DAI by head rotational acceleration were treated with vehicle or curcumin to evaluate the effect of curcumin on neuronal and axonal injury. We observed that curcumin (20 mg/kg intraperitoneal) administered 1 h after DAI induction alleviated the aggregation of p-tau and β-APP in neurons, reduced ER-stress-related cell apoptosis, and ameliorated neurological deficits. Further investigation showed that the protective effect of curcumin in DAI was mediated by the PERK/Nrf2 pathway. Curcumin promoted PERK phosphorylation, and then Nrf2 dissociated from Keap1 and was translocated to the nucleus, which activated ATF4, an important bZIP transcription factor that maintains intracellular homeostasis, but inhibited the CHOP, a hallmark of ER stress and ER-associated programmed cell death. In summary, we demonstrate for the first time that curcumin confers protection against abnormal proteins and neuronal apoptosis after DAI, that the process is mediated by strengthening of the unfolded protein response to overcome ER stress, and that the protective effect of curcumin against DAI is dependent on the activation of Nrf2.

Normothermic Machine Perfusion Protects Against Liver Ischemia-Reperfusion Injury During Reduced-Size Liver Transplantation in Pigs

Background

Normothermic machine perfusion (NMP) preservation is superior to cold preservation during reduced-size liver transplantation (RSLT) in pigs. However, the mechanism of this protective effect has not been explained. We aimed to compare the effects of NMP preservation with that of cold preservation (CS) in protecting against ischemia-reperfusion injury (IRI) during RSLT in pigs.

Material/Methods

Twenty-four healthy Bama miniature pigs were randomized into 2 groups: 1) the NMP group in which donor livers harvested without warm ischemia time and cardiac activity were connected to the NMP system to reduce liver size under normothermic conditions, and 2) the CS group in which donor livers harvested without warm ischemia time and cardiac activity were perfused using the University of Wisconsin (UW) solution and then preserved in the 0–4°C UW solution to reduce liver size under cold conditions. Livers were then transplanted without veno-venous bypass. Amounts of bile secretion for the NMP groups were recorded hourly. The serological indices were measured. Expressions of cytochrome C, caspase 3, and NF-κB p65 in liver tissue were observed.

Results

The levels of bile secretions were gradually diminished from 16.50±2.66 mL/h before splitting to 6.35±1.24 mL/h after splitting. With the exception of TNF-α on postoperative day 2, overall, levels of TNF-α, IL-1, IL-6, and MDA were significantly lower in the NMP group versus CS group for all 5 days postoperatively. Finally, cytochrome C, caspase 3, and NF-κB p65 expressions were all significantly suppressed in the NMP group as compared with the CS group.

Conclusions

MP preservation is superior to cold preservation in protecting against liver IRI during RSLT in pigs.

Protective effects of tanshinone IIA on SH-SY5Y cells against oAβ1-42-induced apoptosis due to prevention of endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress caused by β-amyloid protein (Aβ) may play an important role in the pathogenesis of Alzheimer disease (AD). Our previous data have indicated that tanshinone IIA (tan IIA) protected primary neurons from Aβ induced neurotoxicity. To further explore the neuroprotection of tan IIA, here we study the effects of tan IIA on the ER stress response in oligomeric Aβ_1-42 (oAβ_1-42)-induced SH-SY5Y cell injury. Our data showed that tan IIA pretreatment could increase cell viability and inhibit apoptosis caused by oAβ_1-42. Furthermore, tan IIA markedly suppressed ER dilation and prevented oAβ_1-42-induced abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), activating transcription factor 6 (ATF6), as well as inhibited the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways. Moreover, tan IIA ameliorated oAβ_1-42-induced Bcl-2/Bax ratio reduction, prevented cytochrome c translocation into cytosol from mitochondria, reduced oAβ_1-42-induced cleavage of caspase-9 and caspase-3, suppressed caspase-3/7 activity, and increased mitochondrial membrane potential (MMP) and ATP content. Meanwhile, oAβ_1-42-induced cell apoptosis and activation of ER stress can also be attenuated by the inhibitor of ER stress 4-phenylbutyric acid (4-PBA). Taken together, these data indicated that tan IIA protects SH-SY5Y cells against oAβ_1-42-induced apoptosis through attenuating ER stress, modulating CHOP and JNK pathways, decreasing the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3, as well as increasing the ratio of Bcl-2/Bax, MMP and ATP content. Our results strongly suggested that tan IIA may be effective in treating AD associated with ER stress.

CAAT/enhancer binding protein-homologous protein deficiency attenuates liver ischemia/reperfusion injury in mice

Ischemia/reperfusion injury (IRI) is one of the main causes of liver dysfunction after liver surgery. Involvement of endoplasmic reticulum (ER) stress in various diseases has been demonstrated, and CAAT/enhancer binding protein-homologous protein (CHOP) is a transcriptional regulator that is induced by ER stress. It is also a key regulator of ER stress-mediated apoptosis. The aim of this study was to investigate the role of CHOP in liver IRI. Wild type (WT) and CAAT/enhancer binding protein-homologous protein knockout (CHOP-/-) mice were subjected to 70% liver warm ischemia/reperfusion for 60 minutes. At different times after reperfusion, liver tissues and blood samples were collected for evaluation. Induction of ER stress including CHOP expression was ascertained. Liver damage was evaluated based on serum liver enzymes, liver histology, and neutrophil infiltration. Hepatocyte death including apoptosis was assessed. Liver warm IRI induced ER stress in both WT and CHOP-/- mice. In addition, CHOP expression was up-regulated in WT mice. At 6 hours after reperfusion, liver damage was attenuated in CHOP-/- mice. On the basis of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining, apoptotic and necrotic cells were significantly reduced in CHOP-/- mice. CHOP deficiency also reduced the cleavage of caspase 3 and expression of the proapoptotic protein B cell lymphoma 2-associated X protein. Liver IRI induces CHOP expression, and CHOP deficiency attenuates liver IRI by inhibiting apoptosis. Elucidation of the function of CHOP in liver IRI may contribute to further investigation for a therapy against liver IRI associated with the ER stress pathway. Liver Transplantation 24 645-654 2018 AASLD.

Neuronal-like differentiated SH-SY5Y cells adaptation to a mild and transient H2 O2 -induced oxidative stress

Preconditioning (PC) is a cell adaptive response to oxidative stress and, with regard to neurons, can be considered as a neuroprotective strategy. The aim of the present study was to verify how neuronal-like differentiated SH-SY5Y cells adapt to a mild and transient H₂ O₂ -induced oxidative stress and, hence, whether may be considered as more sensitive cell model to study PC pathways. A first screening allowed to define H₂ O₂ concentrations for PC (10μM-50μM), applied before damage(100μM H₂ O₂ ). Cell viability measured 24 hours after 100μM H₂ O₂ -induced damage was ameliorated by 24-hour pre-exposure to low-concentration H₂ O₂ (10μM-30μM) with cell size as well restored. Markers for apoptosis (Bcl-2 and Bad), inflammation (iNOS), and redox system (MnSOD) were also determined, showing that, in cells pre-exposed to 10μM H₂ O₂ and then submitted to 100μM H₂ O₂ , Bcl-2 levels were higher, Bad and iNOS levels were lower than those observed in damaged cells, and MnSOD levels were unchanged. Such findings show that (1) neuronal-like differentiated SH-SY5Y cells are a suitable model to investigate PC response and more sensitive to the effect of a mild and transient H₂ O₂ -induced oxidative stress with respect to other neuronal cells; (2) 10μM H₂ O₂ -induced PC is mediated by apoptotic and inflammatory pathways, unlike antioxidant system; (3) such neuroprotective strategy and underlying signals proven in neuronal-like differentiated SH-SY5Y cells may contribute to understand in vivo PC mechanisms and to define a window for pharmacological intervention, namely, related to ischemic brain damage.

SIGNIFICANCE OF THE STUDY

Neuronal-like differentiated SH-SY5Y cells are a suitable model to investigate PC, an endogenous neuroprotective response to a mild and transient H₂ O₂ -induced oxidative stress, elicited by 24-hour exposure to very low H₂ O₂ concentrations and mediated by both apoptotic and inflammatory pathways. This model reflects in vivo PC mechanisms occurring after brain trauma and provides novel information about pathways and time of protection useful for an appropriate pharmacological intervention.

Acute Limb Ischemia-Much More Than Just a Lack of Oxygen

Acute ischemia of an extremity occurs in several stages, a lack of oxygen being the primary contributor of the event. Although underlying patho-mechanisms are similar, it is important to determine whether it is an acute or chronic event. Healthy tissue does not contain enlarged collaterals, which are formed in chronically malperfused tissue and can maintain a minimum supply despite occlusion. The underlying processes for enhanced collateral blood flow are sprouting vessels from pre-existing vessels (via angiogenesis) and a lumen extension of arterioles (via arteriogenesis). While disturbed flow patterns with associated local low shear stress upregulate angiogenesis promoting genes, elevated shear stress may trigger arteriogenesis due to increased blood volume. In case of an acute ischemia, especially during the reperfusion phase, fluid transfer occurs into the tissue while the vascular bed is simultaneously reduced and no longer reacts to vaso-relaxing factors such as nitric oxide. This process results in an exacerbative cycle, in which increased peripheral resistance leads to an additional lack of oxygen. This whole process is accompanied by an inundation of inflammatory cells, which amplify the inflammatory response by cytokine release. However, an extremity is an individual-specific composition of different tissues, so these processes may vary dramatically between patients. The image is more uniform when broken down to the single cell stage. Because each cell is dependent on energy produced from aerobic respiration, an event of acute hypoxia can be a life-threatening situation. Aerobic processes responsible for yielding adenosine triphosphate (ATP), such as the electron transport chain and oxidative phosphorylation in the mitochondria, suffer first, thus disrupting the integrity of cellular respiration. One consequence of this is irreparable damage of the cell membrane due to an imbalance of electrolytes. The eventual increase in net fluid influx associated with a decrease in intracellular pH is considered an end-stage event. Due to the lack of ATP, individual cell organelles can no longer sustain their activity, thus initiating the cascade pathways of apoptosis via the release of cytokines such as the BCL2 associated X protein (BAX). As ischemia may lead to direct necrosis, inflammatory processes are further aggravated. In the case of reperfusion, the flow of nascent oxygen will cause additional damage to the cell, further initiating apoptosis in additional surrounding cells. In particular, free oxygen radicals are formed, causing severe damage to cell membranes and desoxyribonucleic acid (DNA). However, the increased tissue stress caused by this process may be transient, as radical scavengers may attenuate the damage. Taking the above into final consideration, it is clearly elucidated that acute ischemia and subsequent reperfusion is a process that leads to acute tissue damage combined with end-organ loss of function, a condition that is difficult to counteract.

Effect of dark sweet cherry powder consumption on the gut microbiota, short-chain fatty acids, and biomarkers of gut health in obese db/db mice

Cherries are fruits containing fiber and bioactive compounds (e.g., polyphenolics) with the potential of helping patients with diabetes and weight disorders, a phenomenon likely related to changes in the complex host-microbiota milieu. The objective of this study was to investigate the effect of cherry supplementation on the gut bacterial composition, concentrations of caecal short-chain fatty acids (SCFAs) and biomarkers of gut health using an in vivo model of obesity. Obese diabetic (db/db) mice received a supplemented diet with 10% cherry powder (supplemented mice, n = 12) for 12 weeks; obese (n = 10) and lean (n = 10) mice served as controls and received a standard diet without cherry. High-throughput sequencing of the 16S rRNA gene and quantitative real-time PCR (qPCR) were used to analyze the gut microbiota; SCFAs and biomarkers of gut health were also measured using standard techniques. According to 16S sequencing, supplemented mice harbored a distinct colonic microbiota characterized by a higher abundance of mucin-degraders (i.e., Akkermansia) and fiber-degraders (the S24-7 family) as well as lower abundances of Lactobacillus and Enterobacteriaceae. Overall this particular cherry-associated colonic microbiota did not resemble the microbiota in obese or lean controls based on the analysis of weighted and unweighted UniFrac distance metrics. qPCR confirmed some of the results observed in sequencing, thus supporting the notion that cherry supplementation can change the colonic microbiota. Moreover, the SCFAs detected in supplemented mice (caproate, methyl butyrate, propionate, acetate and valerate) exceeded those concentrations detected in obese and lean controls except for butyrate. Despite the changes in microbial composition and SCFAs, most of the assessed biomarkers of inflammation, oxidative stress, and intestinal health in colon tissues and mucosal cells were similar in all obese mice with and without supplementation. This paper shows that dietary supplementation with cherry powder for 12 weeks affects the microbiota and the concentrations of SCFAs in the lower intestinal tract of obese db/db diabetic mice. These effects occurred in absence of differences in most biomarkers of inflammation and other parameters of gut health. Our study prompts more research into the potential clinical implications of cherry consumption as a dietary supplement in diabetic and obese human patients.

A polysaccharide (PNPA) from Pleurotus nebrodensis ameliorates hepatic ischemic/reperfusion (I/R) injury in rats

The effects of a polysaccharide (PNPA) from the fruiting bodies of Pleurotus nebrodensis on hepatic ischemia/reperfusion (I/R) injury in rats were explored. Severe liver injury was shown in rats following I/R with high content of serum AST and ALT, as evidenced by histological examination, whereas less damage was noted after PNPA treatment compared to rats in the I/R group. Also, pre-treatment with PNPA (400mg/kg) could reduce the level of MDA in liver tissue and increase the activity of ROS scavengers (T-AOC, SOD, CAT, GSH-PX), Nitric oxide synthase (T-NOS and iNOS), and GSH. Moreover, PNPA could still reduce the production of I/R-induced inflammatory cytokines (IL-1β, IL-6, TNF-α and NF-κB) in liver, along with MPO. I/R-induced high level of pro-apoptotic indicators (cytochrome c, Bax, and caspase 3) and low level of anti-apoptotic indicators Bcl-2 were reversed after PNPA pretreatment. Therefore, PNPA might be a promising candidate for preventing hepatic I/R injury.

IRAK-4-shRNA Prevents Ischemia/Reperfusion Injury Via Different Perfusion Periods Through the Portal Vein After Liver Transplantation in Rat

BACKGROUND

This study analyzed the effects of short hairpin RNA targeting interleukin-1 receptor-associated kinase-4 (IRAK-4-shRNA) via portal vein perfusion during different periods on ischemia/reperfusion injury after liver transplantation.

METHODS

Rats were randomly divided into 3 groups: the cold ischemia transfection group (CIT group, n = 18), in which graft livers were perfused with the plasmid of pSIIRAK-4 expressing IRAK-4-shRNA for 4 minutes (0.5 mL/min) via the portal vein during the cold ischemia period; the in vivo transfection group (IVT group, n = 18), in which equivalent volumes (2 mL) of IRAK-4-ShRNA plasmid (pSIIRAK-4) were injected during the operation; and the control group (n = 18), in which the rats received equivalent volumes of blank plasmid. At 0, 60, and 180 minutes after portal vein reperfusion, blood and liver tissues were collected for examination. IRAK-4 expression, nuclear factor kB (NF-kB) activity, tumor necrosis factor α, interleukin (IL)-1β, and IL-6 serum levels, as well as histologic changes, were detected.

RESULTS

At 0 minutes after reperfusion, IRAK-4 expression, NF-κB activity, and serum levels of tumor necrosis factor α, IL-1β, and IL-6 showed no significant differences among the 3 groups (P > .05). At 60 and 180 minutes after reperfusion, all indices of the IVT and control groups were significantly higher than those of the CIT group (P < .01). Meanwhile, all indices of the CIT group showed no significant differences at various time points (P > .05). Liver function and histologic changes exhibited less liver injury in the CIT group than in the other groups.

CONCLUSIONS

IRAK-4 activity was suppressed by IRAK-4-shRNA through portal vein perfusion during the cold ischemia period, and IRAK-4-shRNA effectively prevented ischemia/reperfusion injury after liver transplantation.

Remote Ischemic Preconditioning Enhances the Expression of Genes Encoding Antioxidant Enzymes and Endoplasmic Reticulum Stress-Related Proteins in Rat Skeletal Muscle

Purpose:

Ischemic preconditioning (IPC), including remote IPC (rIPC) and direct IPC (dIPC), is a promising method to decrease ischemia-reperfusion (IR) injury. This study tested the effect of both rIPC and dIPC on the genes for antioxidant enzymes and endoplasmic reticulum (ER) stress-related proteins.

Materials and Methods:

Twenty rats were randomly divided into the control and study groups. In the control group (n=10), the right hind limb was sham-operated. The left hind limb (IscR) of the control group underwent IR injury without IPC. In the study group (n=10), the right hind limb received IR injury after 3 cycles of rIPC. The IscR received IR injury after 3 cycles of dIPC. Gene expression was analyzed by Quantitative real-time polymerase chain reaction from the anterior tibialis muscle.

Results:

The expression of the antioxidant enzyme genes including glutathione peroxidase (GPx), superoxide dismutase (SOD) 1 and catalase (CAT) were significantly reduced in IscR compared with sham treatment. In comparison with IscR, rIPC enhanced the expression of GPx, SOD2, and CAT genes. dIPC enhanced the expression of SOD2 and CAT genes. The expression of SOD2 genes was consistently higher in rIPC than in dIPC, but the difference was only significant for SOD2. The expression of genes for ER stress-related proteins tended to be reduced in IscR in comparison with sham treatment. However, the difference was only significant for C/EBP homologous protein (CHOP). In comparison with IscR, rIPC significantly up-regulated activating transcription factor 4 and CHOP, whereas dIPC up-regulated CHOP.

Conclusion:

Both rIPC and dIPC enhanced expression of genes for antioxidant enzymes and ER stress-related proteins.

Down-Regulated Receptor Interacting Protein 140 Is Involved in Lipopolysaccharide-Preconditioning-Induced Inactivation of Kupffer Cells and Attenuation of Hepatic Ischemia Reperfusion Injury

Background

Lipopolysaccharide (LPS) preconditioning is known to attenuate hepatic ischemia/reperfusion injury (I/RI); however, the precise mechanism remains unclear. This study investigated the role of receptor-interacting protein 140 (RIP140) on the protective effect of LPS preconditioning in hepatic I/RI involving Kupffer cells (KCs).

Methods

Sprague—Dawley rats underwent 70% hepatic ischemia for 90 minutes. LPS (100 μg/kg) was injected intraperitoneally 24 hours before ischemia. Hepatic injury was observed using serum and liver samples. The LPS/NF-κB (nuclear factor-κB) pathway and hepatic RIP140 expression in isolated KCs were investigated.

Results

LPS preconditioning significantly inhibited hepatic RIP140 expression, NF-κB activation, and serum proinflammatory cytokine expression after I/RI, with an observation of remarkably reduced serum enzyme levels and histopathologic scores. Our experiments showed that protection effects could be effectively induced in KCs by LPS preconditioning, but couldn’t when RIP140 was overexpressed in KCs. Conversely, even without LPS preconditioning, protective effects were found in KCs if RIP140 expression was suppressed with siRNA.

Conclusions

Down-regulated RIP140 is involved in LPS-induced inactivation of KCs and hepatic I/RI attenuation.

Oleanolic acid attenuates liver ischemia reperfusion injury by HO-1/Sesn2 signaling pathway

BACKGROUND

Ischemia reperfusion injury (IRI) is unavoidable in liver transplantation and hepatectomy. The present study aimed to explore the possible mechanism and the effect of oleanolic acid (OA) in hepatic IRI.

METHODS

Mice were randomly divided into 6 groups based on different treatment. IRI model: The hepatic artery, portal vein, and bile duct to the left and median liver lobes (70% of the liver) were occluded with an atraumatic bulldog clamp for 90 minutes and then the clamp was removed for reperfusion. The mice were sacrificed 6 hours after reperfusion, and blood and liver tissues were collected. Liver injury was evaluated by biochemical and histopathologic examinations. The expressions of Sesn2, PI3K, Akt and heme oxygenase-1 (HO-1) were measured with quantitative real-time RT-PCR and Western blotting.

RESULTS

The serum aminotransferases level and scores of hepatic histology were increased after reperfusion. The increase was attenuated by pretreatment with OA (P<0.01). Compared with the IR group, OA pretreatment significantly up-regulated the expression of Sesn2, PI3K, Akt and HO-1 in IR livers (P<0.05). Administration of zinc protoporphyrin (ZnPP), an inhibitor of HO-1, diminished the OA effect on HO-1 and Sesn2 expressions (P<0.05) and the protective effect of OA on IRI.

CONCLUSIONS

Our results demonstrate that OA can attenuate hepatic IRI. The protective mechanism may be related to the OA-induced HO-1/Sesn2 signaling pathway.

Preconditioning by Low Dose LPS Prevents Subsequent LPS-Induced Severe Liver Injury via Nrf2 Activation in Mice

BACKGROUND

Sepsis is a syndrome triggered by endotoxin lipopolysaccharide (LPS) during bacterial infection. Sepsis sometimes recurs, with the second sepsis giving rise to a different phenotype because of disease modification by the preceding sepsis. Such a protective modification is called a preconditioning (PC) effect. PC is an endogenous protective mechanism by which sublethal damage confers tolerance to a subsequent lethal load. Oxidative stress is one of the important pathogenetic mechanisms that occur in sepsis. The nuclear factor erythroid 2 (NF-E2)-related factor-2 (Nrf2) system is a key regulatory transcription factor that protects organs and cells against oxidative stress and may be associated with the PC effect in repeated sepsis.

METHODS

The effect of PC induced by low-dose LPS on survival rate and liver injury against subsequent high-dose LPS stimulation was examined using a mouse model of sepsis. In order to understand the detailed mechanism(s) involved in the PC effect within the liver, gene expression array was performed. As a candidate mechanism of PC, the activation of the Nrf2 system was analyzed using Nrf2 reporter mice. Furthermore, the induction of heme oxygenase-1 (HO-1), one of the main targets of Nrf2, in the liver was examined by immunoblotting and immunohistochemistry. The PC effect on liver injury induced by LPS was further examined using Nrf2-deficient mice.

RESULTS

PC by LPS (1.7 or 5.0 mg/kg body weight, intraperitoneally) increased the survival rate of mice and decreased liver injury in response to a subsequent injection of a lethal level of LPS (20 mg/kg body weight). DNA array revealed that the gene ontology term "antioxidant activity" as one of the candidate mechanisms of the PC effect by LPS. In Nrf2 reporter mice, PC immediately and intensely enhanced luminescence that indicated Nrf2 activation after subsequent LPS injection. The induction of HO-1 by LPS was also enhanced by preceding PC, and its induction was observed mainly in Kupffer cells of the liver. In Nrf2-deficient mice, the induction of HO-1 in Kupffer cells and the hepatoprotective effect of PC were decreased as compared with wild-type mice.

CONCLUSION

Our results suggest that activation of the Nrf2 system is, at least in part, one of the mechanisms of a PC effect in the mouse liver in the case of repeated LPS stimulation.

Short-term starvation attenuates liver ischemia-reperfusion injury (IRI) by Sirt1-autophagy signaling in mice

Calorie restriction or starvation (fasting) has some beneficial effects in terms of prolonging life and increasing resistance to stress. It has also been shown that calorie restriction has a protective role during ischemia-reperfusion injury (IRI) in several organs, but the underlying mechanism has not been elucidated. In this study we investigated the effects and molecular mechanisms of short-term starvation (STS) on liver IRI in a mouse liver IRI model. We found that STS significantly attenuated liver IRI in this model, as evidenced by inhibition of serum aminotransferase levels, and decreased pathological damage and hepatocellular apoptosis, especially after 2- or 3-day starvation. Furthermore, we found that 2- or 3-day starvation induced expression of hepatocellular autophagy in vivo and in vitro. Further experiments provided support for the notion that STS-induced autophagy played a key role during starvation-regulated protection against liver IRI via autophagy inhibition with 3-methyladenine. Interestingly, the longevity gene Sirt1 was also significantly up-regulated in liver after STS. Importantly, inhibition of Sirt1 by sirtinol abolished STS-induced autophagy and further abrogated STS-mediated protection against liver IRI. In conclusion, our results indicate that STS attenuates liver IRI via the Sirt1-autophagy pathway. Our findings provide a rationale for a novel therapeutic strategy for managing liver IRI.

Ischemic Preconditioning protects hepatocytes from ischemia-reperfusion injury via TGR5-mediated anti-apoptosis

Ischemic preconditioning (IP) has been shown to protect hepatic tissue from liver ischemia-reperfusion injury (IRI). TGR5, as a new-type bile acid receptor, has been shown protective roles in several liver diseases. However, the relationship between TGR5 and IP is still unknown. This study investigated effects of IP on TGR5 as well as the roles of TGR5 on hepatic tissue lesions and apoptosis in liver IRI. We showed that TGR5 was significantly upregulated in liver tissues after IP. To further analyzed effects of the TGR5 on liver IRI, wild type and TGR5 knockout mice were used to establish the liver IRI model. IP effectively alleviated liver IRI, but TGR5 deficiency significantly neutralized IP-related liver protection, as evidenced by serum alanine aminotransferase levels, histological liver damage, hepatocellular apoptosis and cytokines expressions. In addition, molecules related to apoptosis were detected by Western Blot, which showed that activation of TGR5 by IP increased expression of Bcl-2, and inhibited expressions of IRAK4 and cleaved caspase-3, but TGR5 deficiency abolished IP-induced expressions of anti-apoptosis molecule. In vitro, effects of TGR5 on hepatocytes were further analyzed by TGR5 agonist (INT-777) and hypoxia/reoxygenation (H/R), which displayed that INT-777 markedly attenuated H/R-induced hepatocellular apoptosis. In conclusion, our study indicates that IP alleviates hepatocellular apoptosis, and reduces liver IRI through TGR5-mediated anti-apoptosis functions.

Effects of melatonin on liver function and lipid peroxidation in a rat model of hepatic ischemia/reperfusion injury

The present study aimed to investigate the effects of melatonin (MT) on liver function and lipid peroxidation following hepatic ischemia-reperfusion injury (IRI). A total of 66 male Sprague-Dawley rats were randomly assigned into three groups: Normal control (N) group, ischemia-reperfusion (IR) group and the MT-treated group. A hepatic IRI model was developed by blocking the first porta hepatis, and subsequently restoring hepatic blood inflow after 35 min. Following reperfusion, changes in the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) were detected by a chemical method at various time points. In the MT group, the MDA levels were significantly reduced (P<0.05) at all time points, as compared with the IR group. Furthermore, SOD activity was significantly increased (P<0.05) in the MT group, as compared with the IR group at all time points; and the levels of GSH in the MT group were significantly higher (P<0.05) than those of the IR group at 2, 4, and 8 h post-reperfusion. The levels of ALT, AST and LDH were significantly reduced in the MT group at each time point, as compared with that of the IR group (P<0.05). In conclusion, MT exhibits potent antioxidant properties that may create favorable conditions for the recovery of liver function following IRI.

Protective role of silent information regulator 1 against hepatic ischemia: effects on oxidative stress injury, inflammatory response, and MAPKs

OBJECTIVE

Previous studies have verified that silent information regulator 1 (SIRT1), a class III histone deacetylase, protects against ischemia reperfusion (IR) injury (IRI) in some organs. In this study, we examined whether SIRT1 could protect against hepatic IRI and explored the potential mechanisms.

RESEARCH DESIGN AND METHODS

We examined whether SIRT1 could protect against hepatic IRI in vivo and in vitro using hepatic-specific SIRT1(-/-) mice, SIRT1 siRNA-transfected hepatocytes and SIRT1(+/+) hepatocytes.

RESULTS

The expression and activity of SIRT1 were significantly reduced during reperfusion compared with that observed in the control group. Hepatic-specific SIRT1(-/-) mice exhibited significant increase of hepatic damage markers and augment of oxidative stress and inflammatory response compared with control mice. In vitro studies demonstrated similar results. Furthermore, SIRT1 upregulation protects against hepatic IRI, through the overexpression of p-JNK, p-p38MAPK, and p-ERK. The protection of SIRT1 can be effectively reversed by the inhibitors of p38MAPK, JNK, and ERK.

CONCLUSION

The activation of SIRT1 significantly inhibits the oxidative stress and inflammatory response during hepatic IRI, which can be developed as a novel method to protect against hepatic IRI.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.

IL-11 Attenuates Liver Ischemia/Reperfusion Injury (IRI) through STAT3 Signaling Pathway in Mice

Background

The protective role of IL-11, an IL-6 family cytokine, has been implicated in ischemia/reperfusion injury (IRI) in the heart and kidney, but its role has not been elucidated in liver IRI. This study was designed to evaluate the effects of IL-11 and its mechanism of action on liver IRI in a mouse model.

Methods

A partial (70%) warm liver IRI was induced by interrupting the artery/portal vein blood supply to the left/middle liver lobes. IL-11 mRNA expression of ischemic liver after reperfusion was analyzed. Signal transducer and activator of transcription 3 (STAT3) was analyzed following IL-11 treatment in vivo and in vitro. Next, IL-11 was injected intraperitoneally (ip) 1 hour before ischemia. Liver injury was assessed based on serum alanine aminotransferase levels and histopathology. Apoptosis and inflammation were also determined in the ischemic liver. To analyze the role of STAT3 in IL-11 treatment, STAT3 siRNA or non-specific (NS) siRNA was used in vitro and in vivo.

Results

IL-11 mRNA expression was significantly increased after reperfusion in the ischemic liver. STAT3, as a target of IL-11, was activated in hepatocytes after IL-11 treatment in vivo and in vitro. Next, effects of IL-11/STAT3 signaling pathway were assessed in liver IRI, which showed IL-11 treatment significantly attenuated liver IRI, as evidenced by reduced hepatocellular function and hepatocellular necrosis/apoptosis. In addition, IL-11 treatment significantly inhibited the gene expressions of pro-inflammatory cytokines (TNF-α and IL-10) and chemokines (IP-10 and MCP-1). To determine the role of STAT3 in the hepatoprotective effects of IL-11, STAT3 siRNA or NS siRNA was used prior to IL-11 treatment. The results showed STAT3 knockdown abrogated the protective effects of IL-11 in vitro and in vivo.

Conclusions

This work provides first-time evidence for the protective effect of IL-11 treatment on hepatocyte in liver IRI, through the activation of the STAT3 pathway.

C/EBP homologous protein (CHOP) contributes to hepatocyte death via the promotion of ERO1α signalling in acute liver failure

CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) has been shown to be a key molecule in endoplasmic reticulum (ER) stress-mediated apoptosis. ER oxidoreductin 1-α (ERO1α), a target of CHOP, is an important oxidizing enzyme that regulates reactive oxygen species (ROS), which play a prominent role in hepatocellular death during acute liver failure (ALF). However, little is known about how CHOP facilitates ROS-induced hepatocellular injury. The present study was designed to investigate the roles and molecular mechanisms of CHOP in ALF. In the liver tissues from ALF patients, the expression of CHOP was significantly increased, which was accompanied by increased expression of dsRNA-dependent protein kinase (PKR)-like ER kinase (PERK) signalling, activating transcription factor 4 (ATF6) signalling, inositol-requiring enzyme-1 (IRE1) signalling and ERO1α, as compared with healthy controls. In the mouse model of galactosamine (GaIN)/lipopolysaccharide (LPS)-induced ALF, the hepatocellular injury was accompanied by up-regulated PERK signalling, ATF6 signalling, IRE1 signalling, CHOP and ERO1α. In contrast, CHOP deficiency decreased hepatocellular apoptosis/necrosis and increased animal survival. Furthermore, disruption of CHOP decreased ERO1α expression leading to reducing ROS-induced cell death in vivo and in vitro. Interestingly, ERO1α overexpression restored GaIN/LPS-induced hepatocellular injury in CHOP-deficient mice. Our studies demonstrate for the first time that CHOP promotes liver damage during ALF through activation of ERO1α, a key mediator to link ER stress and ROS. Therefore, targeting CHOP/ERO1α signalling could be a novel therapeutic approach during ALF.

'Preconditioning' with low dose lipopolysaccharide aggravates the organ injury / dysfunction caused by hemorrhagic shock in rats

Methods

Male rats were ‘pretreated’ with phosphate-buffered saline (PBS; i.p.) or LPS (1 mg/kg; i.p.) 24 h prior to HS. Mean arterial pressure (MAP) was maintained at 30 ± 2 mmHg for 90 min or until 25% of the shed blood had to be re-injected to sustain MAP. This was followed by resuscitation with the remaining shed blood. Four hours after resuscitation, parameters of organ dysfunction and systemic inflammation were assessed.

Results

HS resulted in renal dysfunction, and liver and muscular injury. At a first glance, LPS preconditioning attenuated organ dysfunction. However, we discovered that HS-rats that had been preconditioned with LPS (a) were not able to sustain a MAP at 30 mmHg for more than 50 min and (b) the volume of blood withdrawn in these animals was significantly less than in the PBS-control group. This effect was associated with an enhanced formation of the nitric oxide (NO) derived from inducible NO synthase (iNOS). Thus, a further control group in which all animals were resuscitated after 50 min of hemorrhage was performed. Then, LPS preconditioning aggravated both circulatory failure and organ dysfunction. Most notably, HS-rats pretreated with LPS exhibited a dramatic increase in NF-κB activation and pro-inflammatory cytokines.

Conclusion

In conclusion, LPS preconditioning predisposed animals to an earlier vascular decompensation, which may be mediated by an excess of NO production secondary to induction of iNOS and activation of NF-κB. Moreover, LPS preconditioning increased the formation of pro-inflammatory cytokines, which is likely to have contributed to the observed aggravation of organ injury/dysfunction caused by HS.

N-acetylcysteine attenuates reactive-oxygen-species-mediated endoplasmic reticulum stress during liver ischemia-reperfusion injury

AIM: To investigate the effects of N-acetylcysteine (NAC) on endoplasmic reticulum (ER) stress and tissue injury during liver ischemia reperfusion injury (IRI).

METHODS: Mice were injected with NAC (300 mg/kg) intraperitoneally 2 h before ischemia. Real-time polymerase chain reaction and western blotting determined ER stress molecules (GRP78, ATF4 and CHOP). To analyze the role of NAC in reactive oxygen species (ROS)-mediated ER stress and apoptosis, lactate dehydrogenase (LDH) was examined in cultured hepatocytes treated by H₂O₂ or thapsigargin (TG).

RESULTS: NAC treatment significantly reduced the level of ROS and attenuated ROS-induced liver injury after IRI, based on glutathione, malondialdehyde, serum alanine aminotransferase levels, and histopathology. ROS-mediated ER stress was significantly inhibited in NAC-treated mice. In addition, NAC treatment significantly reduced caspase-3 activity and apoptosis after reperfusion, which correlated with the protein expression of Bcl-2 and Bcl-xl. Similarly, NAC treatment significantly inhibited LDH release from hepatocytes treated by H₂O₂ or TG.

CONCLUSION: This study provides new evidence for the protective effects of NAC treatment on hepatocytes during IRI. Through inhibition of ROS-mediated ER stress, NAC may be critical to inhibit the ER-stress-related apoptosis pathway.

Effect of exercise intensity on unfolded protein response in skeletal muscle of rat

Endoplasmic reticulum (ER) stress, unfolded protein response (UPR), and mitochondrial biogenesis were assessed following varying intensities of exercise training. The animals were randomly assigned to receive either low- (LIT, n=7) or high intensity training (HIT, n=7), or were assigned to a control group (n=7). Over 5 weeks, the animals in the LIT were exercised on a treadmill with a 10° incline for 60 min at a speed of 20 m/min group, and in the HIT group at a speed of 34 m/min for 5 days a week. No statistically significant differences were found in the body weight, plasma triglyceride, and total cholesterol levels across the three groups, but fasting glucose and insulin levels were significantly lower in the exercise-trained groups. Additionally, no statistically significant differences were observed in the levels of PERK phosphorylation in skeletal muscles between the three groups. However, compared to the control and LIT groups, the level of BiP was lower in the HIT group. Compared to the control group, the levels of ATF4 in skeletal muscles and CHOP were significantly lower in the HIT group. The HIT group also showed increased PGC-1α mRNA expression in comparison with the control group. Furthermore, both of the trained groups showed higher levels of mitochondrial UCP3 than the control group. In summary, we found that a 5-week high-intensity exercise training routine resulted in increased mitochondrial biogenesis and decreased ER stress and apoptotic signaling in the skeletal muscle tissue of rats.

DDIT3 overexpression increases odontoblastic potential of human dental pulp cells

OBJECTIVES

Human dental pulp cells (HDPCs) with multi-potential differentiational capacity can undergo odontoblastic differentiation when stimulated with proinflammatory cytokines. However, factors linking proinflammatory stimuli and their odontoblastic differentiation have, as yet, not been completely understood. As an apoptotic transcription factor, DDIT3 plays a crucial role in the inflammatory reaction and in osteogenic differentiation. Thus, we hypothesized that DDIT3 may participate in odontoblastic differentiation of HDPCs.

MATERIALS AND METHODS

Immunofluorescent staining was used to detect expression of DDIT3 in HDPCs and effects of TNFα, on its nuclear accumulation. HDPCs that overexpressed DDIT3 were developed and their proliferation and odontoblastic differentiation abilities were examined. qRT-PCR was employed to detect mineralization-related genes, including ALP, runt-related transcription factor-2 (Runx2), osterix (OSX), dentin sialophosphoprotein (DSPP), dentin matrix acidic phosphoprotein 1 (DMP1) and osteocalcin (OCN). Western blot analysis was performed to detect expression of DSPP protein.

RESULTS

DDIT3 was expressed in HDPCs. TNFα treatment enhanced mRNA expression as well as nuclear accumulation of DDIT3 (slightly). DDIT3 overexpression reduced HDPC proliferation, however, it increased their calcium nodule formation and expression of OSX, DSPP, DMP1 and OCN.

CONCLUSIONS

DDIT3 may be a factor that links proinflammatory stimuli and differentiation of HDPCs.

Vitamin D ameliorates hepatic ischemic/reperfusion injury in rats

Vitamin D, most commonly associated with the growth and remodeling of bone, has been shown to ameliorate ischemia/reperfusion injury (IRI) in some tissues, yet its underlying mechanism remains elusive. This study was designed to examine the protective effect of vitamin D, if any, against hepatic IRI in rats and the underlying mechanism involved. Adult female Wistar rats were randomly divided into control, sham-operated (sham), ischemia/reperfusion (I/R), and ischemic-reperfused vitamin D-treated (vit D) groups. Rats in the I/R and vit D groups were subjected to partial (70%) hepatic ischemia for 45 min, followed by 1 h of reperfusion. Vitamin D was given to rats orally in a dose of 500 IU/kg daily for 2 weeks before being subjected to I/R. Markers of liver damage, oxidative stress, inflammation and apoptosis were evaluated. Hepatic morphology was also examined. Vit D-treated rats had significantly lower serum levels of alanine aminotransferase, aspartate aminotransferase, and γ glutamyl transferase compared to rats in the I/R group. Also, vit D-treated rats showed a significant decrease in malondialdehyde, interleukin-1 beta, interleukin-6, tumor necrosis factor-α, nuclear factor κB, B cell leukemia/lymphoma 2-associated X protein, cytochrome c, and caspase-3 levels, with higher levels of glutathione peroxidase and B cell lymphoma 2 protein levels in liver tissues compared to I/R rats. Histological examination showed less damaged liver tissues with amelioration of apoptotic signs in the vit D group compared to the I/R group. In conclusion, vitamin D supplementation ameliorates hepatic IRI mostly by alleviating the inflammatory-apoptotic response mediated by the oxidative reperfusion injury insult.