Cyclooxygenase-2 deficiency enhances Th2 immune responses and impairs neutrophil recruitment in hepatic ischemia/reperfusion injury

PGE2 synthesis and signaling in the liver physiology and pathophysiology: An update

The liver plays a central role in systemic metabolism and drug degradation. However, it is highly susceptible to damage due to various factors, including metabolic imbalances, excessive alcohol consumption, viral infections, and drug influences. These factors often result in conditions such as fatty liver, hepatitis, and acute or chronic liver injury. Failure to address these injuries could promptly lead to the development of liver cirrhosis and potentially hepatocellular carcinoma (HCC). Prostaglandin E2 (PGE2) is a metabolite of arachidonic acid that belongs to the class of polyunsaturated fatty acids (PUFA) and is synthesized via the cyclooxygenase (COX) pathway. By binding to its G protein coupled receptors (i.e., EP1, EP2, EP3 and EP4), PGE2 has a wide range of physiological and pathophysiology effects, including pain, inflammation, fever, cardiovascular homeostasis, etc. Recently, emerging studies showed that PGE2 plays an indispensable role in liver health and disease. This review focus on the research progress of the role of PGE2 synthase and its receptors in liver physiological and pathophysiological processes and discuss the possibility of developing liver protective drugs targeting the COXs/PGESs/PGE2/EPs axis.

Resolving candidate genes of duck ovarian tissue transplantation via RNA-Seq and expression network analyses

This study aims to identify candidate genes related to ovarian development after ovarian tissue transplantation through transcriptome sequencing (RNA-seq) and expression network analyses, as well as to provide a reference for determining the molecular mechanism of improving ovarian development following ovarian tissue transplantation. We collected ovarian tissues from 15 thirty-day-old ducks and split each ovary into 4 equal portions of comparable sizes before orthotopically transplanting them into 2-day-old ducks. Samples were collected on days 0 (untransplanted), 3, 6, and 9. The samples were paraffin sectioned and then subjected to Hematoxylin-Eosin (HE) staining and follicular counting. We extracted RNA from ovarian samples via the Trizol method to construct a transcriptome library, which was then sequenced by the Illumina Novaseq 6000 sequencing platform. The sequencing results were examined for differentially expressed genes (DEG) through gene ontology (GO) function and the Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses, gene set enrichment analysis (GSEA), weighted correlation network analysis (WGCNA), and protein-protein interaction (PPI) networks. Some of the candidate genes were selected for verification using real-time fluorescence quantitative PCR (qRT-PCR). Histological analysis revealed a significant reduction in the number of morphologically normal follicles at 3, 6, and 9 d after ovarian transplantation, along with significantly higher abnormality rates (P < 0.05). The transcriptome analysis results revealed 2,114, 2,224, and 2,257 upregulated DEGs and 2,647, 2,883, and 2,665 downregulated DEGs at 3, 6, and 9 d after ovarian transplantation, respectively. Enrichment analysis revealed the involvement multiple pathways in inflammatory signaling, signal transduction, and cellular processes. Furthermore, WGCNA yielded 13 modules, with 10, 4, and 6 candidate genes mined at 3, 6 and 9 d after ovarian transplantation, respectively. Transcription factor (TF) prediction showed that STAT1 was the most important TF. Finally, the qRT-PCR verification results revealed that 12 candidate genes exhibited an expression trend consistent with sequencing data. In summary, significant differences were observed in the number of follicles in duck ovaries following ovarian transplantation. Candidate genes involved in ovarian vascular remodeling and proliferation were screened using RNA-Seq and WGCNA.

High-mannose glycans from Schistosoma mansoni eggs are important for priming of Th2 responses via Dectin-2 and prostaglandin E2

The parasitic helminth Schistosoma mansoni is a potent inducer of type 2 immune responses by stimulating dendritic cells (DCs) to prime T helper 2 (Th2) responses. We previously found that S. mansoni soluble egg antigens (SEA) promote the synthesis of Prostaglandin E2 (PGE2) by DCs through ERK-dependent signaling via Dectin-1 and Dectin-2 that subsequently induces OX40L expression, licensing them for Th2 priming, yet the ligands present in SEA involved in driving this response and whether specific targeting of PGE2 synthesis by DCs could affect Th2 polarization are unknown. We here show that the ability of SEA to bind Dectin-2 and drive ERK phosphorylation, PGE2 synthesis, OX40L expression, and Th2 polarization is impaired upon cleavage of high-mannose glycans by Endoglycosidase H treatment. This identifies high-mannose glycans present on glycoproteins in SEA as important drivers of this signaling axis. Moreover, we find that OX40L expression and Th2 induction are abrogated when microsomal prostaglandin E synthase-1 (mPGES) is selectively inhibited, but not when a general COX-1/2 inhibitor is used. This shows that the de novo synthesis of PGE2 is vital for the Th2 priming function of SEA-stimulated DCs as well as points to the potential existence of other COX-dependent lipid mediators that antagonize PGE2-driven Th2 polarization. Lastly, specific PGE2 inhibition following immunization with S. mansoni eggs dampened the egg-specific Th cell response. In summary, our findings provide new insights in the molecular mechanisms underpinning Th2 induction by S. mansoni and identify druggable targets for potential control of helminth driven-Th2 responses.

Cannabidiol alleviates carbon tetrachloride-induced liver fibrosis in mice by regulating NF-κB and PPAR-α pathways

Liver fibrosis has become a serious public health problem that can develop into liver cirrhosis and hepatocellular carcinoma and even lead to death. Cannabidiol (CBD), which is an abundant nonpsychoactive component in the cannabis plant, exerts cytoprotective effects in many diseases and under pathological conditions. In our previous studies, CBD significantly attenuated liver injury induced by chronic and binge alcohol in a mouse model and oxidative bursts in human neutrophils. However, the effects of CBD on liver fibrosis and the underlying mechanisms still need to be further explored. A mouse liver fibrosis model was induced by carbon tetrachloride (CCl4) for 10 weeks and used to explore the protective properties of CBD and related molecular mechanisms. After the injection protocol, serum samples and livers were used for molecular biology, biochemical and pathological analyses. The results showed that CBD could effectively improve liver function and reduce liver damage and liver fibrosis progression in mice; the expression levels of transaminase and fibrotic markers were reduced, and histopathological characteristics were improved. Moreover, CBD inhibited the levels of inflammatory cytokines and reduced the protein expression levels of p-NF-κB, NF-κB, p-IκBα, p-p38 MAPK, and COX-2 but increased the expression level of PPAR-α. We found that CBD-mediated protection involves inhibiting NF-κB and activating PPAR-α. In conclusion, these results suggest that the hepatoprotective effects of CBD may be due to suppressing the inflammatory response in CCl4-induced mice and that the NF-κB and PPAR-α signaling pathways might be involved in this process.

Engineered Knockout of TRPA1 Inhibits Laser-Induced Choroidal Neovascularization Along With Associated TGFβ1 Expression and Neutrophil Infiltration

We examined the effects of gene ablation and chemical inhibition of transient receptor potential ankyrin 1 (TRPA1) on the growth of experimental argon laser-induced choroidal neovascularization (CNV) in mice. CNV was induced in the eyes of 6- to 8-week-old TRPA1-null (knockout [KO]) and wild-type (WT) mice by argon laser irradiation. Gene expression analysis was performed in laser-injured tissues at days 1 and 3. CNV growth was evaluated at day 14. Reciprocal bone marrow transplantation was performed between each genotype to identify the components responsible for either recipient tissue or bone marrow-derived inflammatory cells. Our results show that laser irradiation successfully induced CNV growth at the site of laser injury. The size of induced CNV was significantly smaller in KO mice than in WT mice at day 14, as determined by angiography with fluorescein isothiocyanate-dextran. Invasion of neutrophils, but not macrophages, was suppressed in association with suppression of the expression of transforming growth factor β1 and interleukin 6 in laser-irradiated KO tissue. Bone marrow transplantation indicated that the genotype of the recipient mouse, but not of inflammatory cells, is attributable to the KO phenotype. Systemic administration of a TRPA1 antagonist also reduced the CNV in a WT mouse. In conclusion, TRPA1 signaling in local cells is involved in growth of laser-induced CNV. The phenotype was not attributable to vascular endothelial cells and inflammatory cells. Blocking TRPA1 signal may therefore be a potential treatment strategy for CNV-related ocular diseases.

Advances in Understanding the Role of NRF2 in Liver Pathophysiology and Its Relationship with Hepatic-Specific Cyclooxygenase-2 Expression

Oxidative stress and inflammation play an important role in the pathophysiological changes of liver diseases. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that positively regulates the basal and inducible expression of a large battery of cytoprotective genes, thus playing a key role in protecting against oxidative damage. Cyclooxygenase-2 (COX-2) is a key enzyme in prostaglandin biosynthesis. Its expression has always been associated with the induction of inflammation, but we have shown that, in addition to possessing other benefits, the constitutive expression of COX-2 in hepatocytes is beneficial in reducing inflammation and oxidative stress in multiple liver diseases. In this review, we summarized the role of NRF2 as a main agent in the resolution of oxidative stress, the crucial role of NRF2 signaling pathways during the development of chronic liver diseases, and, finally we related its action to that of COX-2, where it appears to operate as its partner in providing a hepatoprotective effect.

COX-2 Expression in Hepatocytes Improves Mitochondrial Function after Hepatic Ischemia-Reperfusion Injury

Cyclooxygenase 2 (COX-2) is a key enzyme in prostanoid biosynthesis. The constitutive hepatocyte expression of COX-2 has a protective role in hepatic ischemia-reperfusion (I/R) injury (IRI), decreasing necrosis, reducing reactive oxygen species (ROS) levels, and increasing autophagy and antioxidant and anti-inflammatory response. The physiopathology of IRI directly impacts mitochondrial activity, causing ATP depletion and being the main source of ROS. Using genetically modified mice expressing human COX-2 (h-COX-2 Tg) specifically in hepatocytes, and performing I/R surgery on the liver, we demonstrate that COX-2 expression has a beneficial effect at the mitochondrial level. Mitochondria derived from h-COX-2 Tg mice livers have an increased respiratory rate associated with complex I electron-feeding pathways compared to Wild-type (Wt) littermates, without affecting complex I expression or assembly. Furthermore, Wt-derived mitochondria show a loss of mitochondrial membrane potential (ΔΨm) that correlates to increased proteolysis of fusion-related OPA1 through OMA1 protease activity. All these effects are not observed in h-COX-2 Tg mitochondria, which behave similarly to the Sham condition. These results suggest that COX-2 attenuates IRI at a mitochondrial level, preserving the proteolytic processing of OPA1, in addition to the maintenance of mitochondrial respiration.

Lipids in Liver Failure Syndromes: A Focus on Eicosanoids, Specialized Pro-Resolving Lipid Mediators and Lysophospholipids

Lipids are organic compounds insoluble in water with a variety of metabolic and non-metabolic functions. They not only represent an efficient energy substrate but can also act as key inflammatory and anti-inflammatory molecules as part of a network of soluble mediators at the interface of metabolism and the immune system. The role of endogenous bioactive lipid mediators has been demonstrated in several inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, cancer). The liver is unique in providing balanced immunotolerance to the exposure of bacterial components from the gut transiting through the portal vein and the lymphatic system. This balance is abruptly deranged in liver failure syndromes such as acute liver failure and acute-on-chronic liver failure. In these syndromes, researchers have recently focused on bioactive lipid mediators by global metabonomic profiling and uncovered the pivotal role of these mediators in the immune dysfunction observed in liver failure syndromes explaining the high occurrence of sepsis and subsequent organ failure. Among endogenous bioactive lipids, the mechanistic actions of three classes (eicosanoids, pro-resolving lipid mediators and lysophospholipids) in the pathophysiological modulation of liver failure syndromes will be the topic of this narrative review. Furthermore, the therapeutic potential of lipid-immune pathways will be described.

Modulation of Prostanoids Profile and Counter-Regulation of SDF-1α/CXCR4 and VIP/VPAC2 Expression by Sitagliptin in Non-Diabetic Rat Model of Hepatic Ischemia-Reperfusion Injury

Molecular mechanisms underlying the beneficial effect of sitagliptin repurposed for hepatic ischemia-reperfusion injury (IRI) are poorly understood. We aimed to evaluate the impact of IRI and sitagliptin on the hepatic profile of eicosanoids (LC-MS/MS) and expression/concentration (RTqPCR/ELISA) of GLP-1/GLP-1R, SDF-1α/CXCR4 and VIP/VPAC1, VPAC2, and PAC1 in 36 rats. Animals were divided into four groups and subjected to ischemia (60 min) and reperfusion (24 h) with or without pretreatment with sitagliptin (5 mg/kg) (IR and SIR) or sham-operated with or without sitagliptin pretreatment (controls and sitagliptin). PGI₂, PGE₂, and 13,14-dihydro-PGE₁ were significantly upregulated in IR but not SIR, while sitagliptin upregulated PGD₂ and 15-deoxy-12,14-PGJ₂. IR and sitagliptin non-significantly upregulated GLP-1 while Glp1r expression was borderline detectable. VIP concentration and Vpac2 expression were downregulated in IR but not SIR, while Vpac1 was significantly downregulated solely in SIR. IRI upregulated both CXCR4 expression and concentration, and sitagliptin pretreatment abrogated receptor overexpression and downregulated Sdf1. In conclusion, hepatic IRI is accompanied by an elevation in proinflammatory prostanoids and overexpression of CXCR4, combined with downregulation of VIP/VPAC2. Beneficial effects of sitagliptin during hepatic IRI might be mediated by drug-induced normalization of proinflammatory prostanoids and upregulation of PGD₂ and by concomitant downregulation of SDF-1α/CXCR4 and reinstating VIP/VCAP2 signaling.

Integrative Analysis of the Roles of lncRNAs and mRNAs in Itaconate-Mediated Protection Against Liver Ischemia-Reperfusion Injury in Mice

Purpose

Itaconate is well known for its strong anti-inflammatory and antioxidant effect, but little is known about the potential role of long non-coding RNAs (lncRNAs) in the underlying mechanisms of hepatic ischemia-reperfusion (IR) injury. The aim of our study is to identify lncRNAs related to IR injury and itaconate-mediated protection and to demonstrate the mechanism by which itaconate acts in liver IR injury from the new perspective of lncRNAs.

Methods

4-Octyl itaconate (OI), a membrane-permeable derivative of itaconate, was used as a substitute for itaconate in our study. By using a mouse model of hepatic IR injury, serum and liver samples were collected to measure indexes of liver injury. Then, the liver samples of the mice were subjected to RNA sequencing (RNA-seq) and subsequent bioinformatics analysis.

Results

Itaconate attenuated liver IR injury. A total of 138 lncRNAs and 156 messenger RNAs (mRNAs) were markedly differentially expressed in the IR-damaged liver tissues pretreated with OI compared with the matched liver tissues treated with vehicle. Functional analysis indicated that lncRNAs may indirectly participate in the effects of itaconate. Furthermore, 41 mRNAs were examined for the protein-protein interaction (PPI) network analysis, and a key gene cluster was defined. Then, combined the coexpression analysis and the cis and trans regulatory function prediction of lncRNAs, some "candidate" lncRNA-mRNA pairs which might relate to itaconate-mediated liver protection were identified, while the relationship requires future validation.

Conclusion

Our study revealed that itaconate could protect the liver against IR injury and that lncRNAs might play a role in this process. Our study provides a novel way to investigate the mechanism by which itaconate affects hepatic IR injury and exerts its anti-inflammatory and antioxidative stress effects.

Protective effect of parecoxib sodium against ischemia reperfusion‑induced intestinal injury

Ischemia reperfusion (I/R)-induced intestinal injury is a pathophysiological process leading to oxidative stress and inflammatory responses, and revealing its underlying mechanisms is essential for developing therapeutic strategies. Cyclooxygenase (COX) has been reported to be involved in I/R injury. Parecoxib sodium, a selective inhibitor for COX-2, exerts protective effects, such as reducing I/R-induced injuries in the heart, kidney and brain. However, the potential role of parecoxib sodium in protecting the small intestine against I/R-induced injury has rarely been investigated. Therefore, the aim of the present study was to elucidate the effects and potential mechanisms of parecoxib sodium in I/R-induced intestinal injury. In total, 60 Sprague-Dawley rats were randomly divided into four groups: Control (sham operation) group, intestinal I/R group, 10 mg/kg parecoxib sodium-pre-treated I/R (I/R + Pare/10) group and the 20 mg/kg parecoxib sodium-pre-treated I/R (I/R + Pare/20) group. A regular I/R model was established to induce the intestinal injury in rats. Parecoxib sodium at 10 or 20 mg/kg was intraperitoneally administered into rats in both I/R + Pare groups once daily for 5 consecutive days prior to ischemia. Blood samples and small intestinal tissues were collected at 2 h after reperfusion. Changes in the levels of malondialdehyde, nitric oxide, interleukin (IL)-1β, IL-8, intercellular cell adhesion molecule-1 and IL-10, as well as the total antioxidant capacity were determined using ELISA, as were the activities of superoxidase dismutase and myeloperoxidase. Furthermore, the protein expression levels of total caspase-3, cleaved caspase-3, Bcl-2 and Bax were examined via western blot analysis. In addition, the daily survival rate post-reperfusion was examined for 7 days. It was revealed that parecoxib sodium increased the levels of antioxidants and suppressed the intestinal oxidative injury induced by I/R. Moreover, parecoxib sodium downregulated the expression levels of the proinflammatory factors, but upregulated the expression levels of anti-inflammatory factors. The results also demonstrated that parecoxib sodium attenuated I/R-induced apoptosis and increased the survival rate of rats. Thus, administration of parecoxib sodium prior to intestinal I/R attenuated intestinal injury and increased the rat survival rate by inhibiting I/R-induced inflammation, oxidative stress and apoptosis.

Cardiac injury modulates critical components of prostaglandin E2 signaling during zebrafish heart regeneration

The inability to effectively stimulate cardiomyocyte proliferation remains a principle barrier to regeneration in the adult human heart. A tightly regulated, acute inflammatory response mediated by a range of cell types is required to initiate regenerative processes. Prostaglandin E₂ (PGE₂), a potent lipid signaling molecule induced by inflammation, has been shown to promote regeneration and cell proliferation; however, the dynamics of PGE₂ signaling in the context of heart regeneration remain underexplored. Here, we employ the regeneration-competent zebrafish to characterize components of the PGE₂ signaling circuit following cardiac injury. In the regenerating adult heart, we documented an increase in PGE₂ levels, concurrent with upregulation of cox2a and ptges, two genes critical for PGE₂ synthesis. Furthermore, we identified the epicardium as the most prominent site for cox2a expression, thereby suggesting a role for this tissue as an inflammatory mediator. Injury also drove the opposing expression of PGE₂ receptors, upregulating pro-restorative ptger2a and downregulating the opposing receptor ptger3. Importantly, treatment with pharmacological inhibitors of Cox2 activity suppressed both production of PGE₂, and the proliferation of cardiomyocytes. These results suggest that injury-induced PGE₂ signaling is key to stimulating cardiomyocyte proliferation during regeneration.

BPTF cooperates with p50 NF-κB to promote COX-2 expression and tumor cell growth in lung cancer

Cyclooxygenase-2 (COX-2) is overexpressed in most human cancers, but its precise regulatory mechanism in cancer cells remains unclear. The aims of this study are to discover and identify the new regulatory factors which bind to the COX-2 promoter and regulate COX-2 expression and cancer cell growth, and to elucidate the mechanisms of action of these factors in lung cancer. In this study, the COX-2 promoter-binding protein BPTF (bromodomain PHD finger transcription factor) was detected, identified and verified by biotin-streptavidin-agarose pulldown, mass spectrum analysis and chromatin immunoprecipitation (ChIP) in lung cancer cells, respectively. The expressions of COX-2 and BPTF in lung cancer cell lines, mouse tumor tissues and human clinical samples were detected by RT-PCR, Western blot and immunohistochemistry assays. The interaction of BPTF with NF-kB was analyzed by immunoprecipitation and confocal immunofluorescence assays. We discovered and identified BPTF as a new COX-2 promoter-binding protein in human lung cancer cells. Knockdown of BPTF inhibited COX-2 promoter activity and COX-2 expression in lung cancer cells in vitro and in vivo. We also found that BPTF functioned as a transcriptional regulator through its interaction with the p50 subunit of NF-kB. Knockdown of BPTF abrogated the binding of p50 to the COX-2 promoter, while the inhibition of p50 activity abolished the decreased trend of COX-2 expression and lung cancer cell proliferation caused by BPTF silencing. Moreover, we showed that the expressions of BPTF and COX-2 in tumor tissues of lung cancer patients were positively correlated, and high co-expression of BPTF and COX-2 predicted poor prognosis in lung cancer patients. Collectively, our results indicated that BPTF cooperated with p50 NF-κB to regulate COX-2 expression and lung cancer growth, suggesting that the BPTF/p50/COX-2 axis could be a potential therapeutic target for lung cancer.

The Use of Analgesics during Vaccination with a Live Attenuated Yersinia pestis Vaccine Alters the Resulting Immune Response in Mice

The administration of antipyretic analgesics prior to, in conjunction with, or due to sequelae associated with vaccination is a common yet somewhat controversial practice. In the context of human vaccination, it is unclear if even short-term analgesic regimens can significantly alter the resulting immune response, as literature exists to support several scenarios including substantial immune interference. In this report, we used a live attenuated Yersinia pestis vaccine to examine the impact of analgesic administration on the immune response elicited by a single dose of a live bacterial vaccine in mice. Mice were assessed by evaluating natural and provoked behavior, as well as food and water consumption. The resulting immune responses were assessed by determining antibody titers against multiple antigens and assaying cellular responses in stimulated splenocytes collected from vaccinated animals. We observed no substantial benefit to the mice associated with the analgesic administration. Splenocytes from both C57BL/6 and BALB/c vaccinated mice receiving acetaminophen have a significantly reduced interferon-gamma (IFN-γ) recall response. Additionally, there is a significantly lower immunoglobulin (Ig)G2a/IgG1 ratio in vaccinated BALB/c mice treated with either acetaminophen or meloxicam and a significantly lower IgG2c/IgG1 ratio in vaccinated C57BL/6 mice treated with acetaminophen. Taken together, our data indicate that the use of analgesics, while possibly ethically warranted, may hinder the accurate characterization and evaluation of novel vaccine strategies with little to no appreciable benefits to the vaccinated mice.

TSLP protects against liver I/R injury via activation of the PI3K/Akt pathway

Thymic stromal lymphopoietin (TSLP) is a cytokine mainly released by epithelial cells that plays important roles in inflammation, autoimmune disease, and cancer. While TSLP is expressed in the liver at high levels, the role of TSLP in liver ischemia/reperfusion (I/R) injury remains unknown. Experiments were carried out to determine the role of TSLP in liver I/R injury. Wild-type (WT) and TSLP receptor-knockout (TSLPR-/-) mice were subjected to liver partial warm I/R injury. Liver injury was assessed by measuring serum alanine aminotransferase (ALT) level, necrotic areas by liver histology, hepatocyte death, and local hepatic inflammatory responses. Signal pathways were explored in vivo and in vitro to identify possible mechanisms for TSLP in I/R injury. TSLP and TSLPR protein expression increased during liver I/R in vivo and following hepatocyte hypoxia/reoxygenation in vitro. Deletion of TSLPR or neutralization of TSLP with anti-TSLP antibody exacerbated liver injury in terms of serum ALT levels as well as necrotic areas in liver histology. Administration of exogenous recombinant mouse TSLP to WT mice significantly reduced liver damage compared with controls, but failed to prevent I/R injury in TSLPR-/- mice. TSLP induced autophagy in hepatocytes during liver I/R injury. Mechanistically, Akt was activated in WT mice during liver I/R injury. The opposite results were observed in TSLPR-/- mice. In addition, TSLP could directly induce Akt activation in hepatocytes independent of nonparenchymal cells in vitro. Furthermore, the Akt agonist, insulin-like growth factor-1 (IGF-1), prevented I/R injury in TSLPR-/- mice and an Akt inhibitor, LY294002, blocked the protective effects of TSLP in WT mice subjected to I/R. Our data indicate that TSLP protects against liver I/R injury via activation of the PI3K/Akt pathway. Through this pathway, TSLP induces autophagy in hepatocytes. Thus, TSLP is a potent inhibitor of stress-induced hepatocyte necrosis.

Protective Role of Hepatocyte Cyclooxygenase-2 Expression Against Liver Ischemia-Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) remains a serious clinical problem affecting liver transplantation outcomes. IRI causes up to 10% of early organ failure and predisposes to chronic rejection. Cyclooxygenase-2 (COX-2) is involved in different liver diseases, but the significance of COX-2 in IRI is a matter of controversy. This study was designed to elucidate the role of COX-2 induction in hepatocytes against liver IRI. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were subjected to IRI. hCOX-2-Tg mice exhibited lower grades of necrosis and inflammation than Wt mice, in part by reduced hepatic recruitment and infiltration of neutrophils, with a concomitant decrease in serum levels of proinflammatory cytokines. Moreover, hCOX-2-Tg mice showed a significant attenuation of the IRI-induced increase in oxidative stress and hepatic apoptosis, an increase in autophagic flux, and a decrease in endoplasmic reticulum stress compared to Wt mice. Interestingly, ischemic preconditioning of Wt mice resembles the beneficial effects observed in hCOX-2-Tg mice against IRI due to a preconditioning-derived increase in endogenous COX-2, which is mainly localized in hepatocytes. Furthermore, measurement of prostaglandin E₂ (PGE₂ ) levels in plasma from patients who underwent liver transplantation revealed a significantly positive correlation of PGE₂ levels and graft function and an inverse correlation with the time of ischemia. Conclusion: These data support the view of a protective effect of hepatic COX-2 induction and the consequent rise of derived prostaglandins against IRI.

Inhibition of microsomal prostaglandin E synthase-1 facilitates liver repair after hepatic injury in mice

BACKGROUND & AIMS

Liver repair following hepatic ischemia/reperfusion (I/R) injury is crucial to survival. This study aims to examine the role of endogenous prostaglandin E₂ (PGE₂) produced by inducible microsomal PGE synthase-1 (mPGES-1), a terminal enzyme of PGE₂ generation, in liver injury and repair following hepatic I/R.

METHODS

mPGES-1 deficient (Ptges^-/-) mice or their wild-type (WT) counterparts were subjected to partial hepatic ischemia followed by reperfusion. The role of E prostanoid receptor 4 (EP4) was then studied using a genetic knockout model and a selective antagonist.

RESULTS

Compared with WT mice, Ptges^-/- mice exhibited reductions in alanine aminotransferase (ALT), necrotic area, neutrophil infiltration, chemokines, and proinflammatory cytokine levels. Ptges^-/- mice also showed promoted liver repair and increased Ly6C^low macrophages (Ly6C^low/CD11b^high/F4/80^high-cells) with expression of anti-inflammatory and reparative genes, while WT mice exhibited delayed liver repair and increased Ly6C^high macrophages (Ly6C^high/CD11b^high/F4/80^low-cells) with expression of proinflammatory genes. Bone marrow (BM)-derived mPGES-1-deficient macrophages facilitated liver repair with increases in Ly6C^low macrophages. In vitro, mPGES-1 was expressed in macrophages polarized toward the proinflammatory profile. Mice treated with the mPGES-1 inhibitor Compound III displayed increased liver protection and repair. Hepatic I/R enhanced the hepatic expression of PGE receptor subtype, EP4, in WT mice, which was reduced in Ptges^-/- mice. A selective EP4 antagonist and genetic deletion of Ptger4, which codes for EP4, accelerated liver repair. The proinflammatory gene expression was upregulated by stimulation of EP4 agonist in WT macrophages but not in EP4-deficient macrophages.

CONCLUSIONS

These results indicate that mPGES-1 regulates macrophage polarization as well as liver protection and repair through EP4 signaling during hepatic I/R. Inhibition of mPGES-1 could have therapeutic potential by promoting liver repair after acute liver injury.

LAY SUMMARY

Hepatic ischemia/reperfusion injury is a serious complication that occurs in liver surgery. Herein, we demonstrated that inducible prostaglandin E₂ synthase (mPGES-1), an enzyme involved in synthesizing prostaglandin E₂, worsens the injury and delays liver repair through accumulation of proinflammatory macrophages. Inhibition of mPGES-1 offers a potential therapy for both liver protection and repair in hepatic ischemia/reperfusion injury.

Effects of a Single Dose of Parecoxib on Inflammatory Response and Ischemic Tubular Injury Caused by Hemorrhagic Shock in Rats

Parecoxib, a selective COX-2 inhibitor, is used to improve analgesia in postoperative procedures. Here we evaluated whether pretreatment with a single dose of parecoxib affects the function, cell injury, and inflammatory response of the kidney of rats subjected to acute hemorrhage. Inflammatory response was determined according to serum and renal tissue cytokine levels (IL-1α, IL-1β, IL-6, IL-10, and TNF-α). Forty-four adult Wistar rats anesthetized with sevoflurane were randomized into four groups: placebo/no hemorrhage (Plc/NH); parecoxib/no hemorrhage (Pcx/NH); placebo/hemorrhage (Plc/H); and parecoxib/hemorrhage (Pcx/H). Pcx groups received a single dose of intravenous parecoxib while Plc groups received a single dose of placebo (isotonic saline). Animals in hemorrhage groups underwent bleeding of 30% of blood volume. Renal function and renal histology were then evaluated. Plc/H showed the highest serum levels of cytokines, suggesting that pretreatment with parecoxib reduced the inflammatory response in rats subjected to hemorrhage. No difference in tissue cytokine levels between groups was observed. Plc/H showed higher percentage of tubular dilation and degeneration, indicating that parecoxib inhibited tubular injury resulting from renal hypoperfusion. Our findings indicate that pretreatment with a single dose of parecoxib reduced the inflammatory response and tubular renal injury without altering renal function in rats undergoing acute hemorrhage.

Study of the protective effect of ischemic and pharmacological preconditioning on hepatic ischemic reperfusion injury induced in rats

Background and Aim

Hepatic ischemia reperfusion injury is the main cause of liver failure following liver surgery, so an effective method is needed to prevent or reduce this hepatic injury. The aim of the present study is to investigate the potential effect of ischemic preconditioning versus pharmacological preconditioning with lisinopril or verapamil for protection against hepatic ischemia reperfusion injury induced in rats.

Methods

Rats were divided into six groups. Group I served as control untreated. Rats of group II were subjected to laparotomy without induction of ischemia reperfusion. Ischemia reperfusion by ligation of the portal trait for 30 min, followed by reperfusion for 2 h, was performed in rats of groups III-VI. Ischemic preconditioning was performed for rats of group IV before induction of ischemia reperfusion. Lisinopril and verapamil was given daily for 3 days before induction of ischemia reperfusion in groups V and VI, respectively. Serum level of liver transaminases and liver malondialdehyde content were measured, and hepatic histopathological examination was assessed.

Results

Induction of ischemia reperfusion resulted in significant elevation of liver transaminases and liver malondialdehyde content associated with significant hepatic histopathological injury that were significantly improved by ischemic preconditioning, lisinopril, or verapamil treatment. Verapamil showed the most significant improvement compared with ischemic preconditioning or lisinopril treatment.

Conclusion

Ischemic preconditioning and pharmacological preconditioning by lisinopril or verapamil can protect against hepatic ischemia reperfusion probably through inhibition of oxidative stress and neutrophil infiltration. The most potent protection is demonstrated by verapamil treatment.

Down-regulation of nuclear HMGB1 reduces ischemia-induced HMGB1 translocation and release and protects against liver ischemia-reperfusion injury

Hepatocyte-specific HMGB1 deletion has been found to worsen the injury and inflammation in liver ischemia-reperfusion injury (IRI), highlighting a role for intracellular HMGB1 in cellular protection. Down-regulation of nuclear HMGB1 by small interfering RNA (siRNA) might not only decrease its injurious extracellular role by reducing its release but also serve to maintain its beneficial intracellular role, thus protecting against IRI. We established a non-lethal liver IRI model in mice via segmental hepatic warm ischemia for 1 h and reperfusion for 6 h. HMGB1-siRNA achieved a reduction of ~60–70% in the nuclear HMGB1 expression in the liver at 48 h post-treatment. Knockdown of nuclear HMGB1 expression dramatically reduced both the degree of nuclear-cytoplasmic translocation of HMGB1 during hepatic ischemia and of HMGB1 release after hepatic reperfusion, resulting in significant preservation of liver function and a marked reduction in pathological damage. Also, HMGB1-siRNA pretreatment markedly inhibited the increases in hepatic expression of TLR4, TLR2, RAGE, TNF-α, IL-1β, IL-6, MCP-1, iNOS, and COX-2 seen in control mice after hepatic reperfusion. We demonstrated for the first time that down-regulation of nuclear HMGB1 reduces ischemia-induced HMGB1 release and protects against liver IRI, which is helpful for better understanding the role of HMGB1 in organ IRI.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

Pretreatment of parecoxib attenuates hepatic ischemia/reperfusion injury in rats

Background

Previous studies showed that cyclooxygenase(COX) was involved in ischemia/reperfusion (I/R) injuries. Parecoxib, a selective inhibitor for COX −2, has been shown to have protective properties in reducing I/R injury in the heart, kidney and brain. The aim of this study was to investigate the effects of parecoxib on hepatic I/R and to explore the underlying mechanisms.

Methods

Fifty-two Sprague–Dawley rats were randomly divided into three groups: the sham-operation (Sham) group, the hepatic ischemia/reperfusion (I/R) group, and the parecoxib pretreated I/R (I/R + Pare) group. Partial warm ischemia was produced in the left and middle hepatic lobes of Sprague–Dawley rats for 60 min, followed by 6 h of reperfusion. Rats in the I/R + Pare group received parecoxib (10 mg/kg) intraperitoneally twice a day for three consecutive days prior to ischemia. Blood and tissue samples from the groups were collected 6 h after reperfusion, and a survival study was performed.

Results

Pretreatment with parecoxib prior to I/R insult significantly reduced I/R-induced elevations of aminotransferases, and significantly improved the histological status of the liver. Parecoxib significantly suppressed inflammatory cascades, as demonstrated by attenuations in TNF-α and IL-6. Parecoxib significantly inhibited iNOS and nitrotyrosine expression after I/R and significantly attenuated I/R-induced apoptosis. The 7-day survival rate was increased by pre-administration of parecoxib.

Conclusions

Administration of parecoxib prior to hepatic I/R attenuates hepatic injury through inhibition of inflammatory response and nitrosative stress.

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.

Protective effect of indomethacin in renal ischemia-reperfusion injury in mice

OBJECTIVE

To evaluate the renoprotection effects of non-steroidal anti-inflammatory drugs (NSAIDs) in renal ischemia-reperfusion injury (IRI) and the cyclooxygenase (COX)-1/2 blockade association by indomethacin (IMT) in the mice model.

METHODS

After the left renal pedicle of mice was clamped, IMT was administrated by intraperitoneal injection with four doses: 1, 3, 5, and 7 mg/kg. Blood and kidney samples were collected 24 h after IRI. The renal functions were assayed by the cytokines and serum creatinine (SCr) using enzyme-linked immunosorbent assay (ELISA) kits. Kidney samples were analyzed by hematoxylin and eosin (H&E) and immunohistochemistry stainings.

RESULTS

The mice administered with 5 mg/kg IMT had a marked reduction in SCr and significantly less tubular damage. The tumor necrosis factor α (TNF-α) activity in renal homogenates and interleukin 6 (IL-6) activity in serum had a marked reduction at doses of 5 and 7 mg/kg IMT. The administration of 3 and 5 mg/kg IMT had a marked reduction in the ratio of thromboxane B2 to 6-keto-prostaglandin F1α. COX-1 and COX-2 stainings were weaker in 5 mg/kg IMT groups than that in the other groups.

CONCLUSIONS

There was a dose response in the IMT function of renal IRI in mice, and IMT had a protective effect in a certain dose range. The effect of IMT on mice IRI was related to COX-1/2 blockades.

Mechanisms of hepatic ischemia-reperfusion injury and protective effects of nitric oxide

Hepatic ischemia-reperfusion injury (IRI) is a pathophysiological event post liver surgery or transplantation and significantly influences the prognosis of liver function. The mechanisms of IRI remain unclear, and effective methods are lacking for the prevention and therapy of IRI. Several factors/pathways have been implicated in the hepatic IRI process, including anaerobic metabolism, mitochondria, oxidative stress, intracellular calcium overload, liver Kupffer cells and neutrophils, and cytokines and chemokines. The role of nitric oxide (NO) in protecting against liver IRI has recently been reported. NO has been found to attenuate liver IRI through various mechanisms including reducing hepatocellular apoptosis, decreasing oxidative stress and leukocyte adhesion, increasing microcirculatory flow, and enhancing mitochondrial function. The purpose of this review is to provide insights into the mechanisms of liver IRI, indicating the potential protective factors/pathways that may help to improve therapeutic regimens for controlling hepatic IRI during liver surgery, and the potential therapeutic role of NO in liver IRI.

The effect of etoricoxib on kidney ischemia-reperfusion injury in rats: a biochemical and immunohistochemical assessment

The purpose of this study was to investigate the effect of etoricoxib on oxidative injury induced with ischemia-reperfusion (I/R) in rat kidney tissue in terms of biochemistry and immunohistochemistry. Male Albino Wistar rats were divided into renal I/R (RIR), 50 mg/kg etoricoxib+RIR (ETO-50), 100 mg/kg etoricoxib+RIR (ETO-100) and sham operation (SG) groups. Animals in the ETO-50 and ETO-100 groups were given etoricoxib by the oral route at dosages of 50 and 100 mg/kg, respectively. The RIR and SG groups were given distilled water as solvent. One hour after drug administration, 1h of ischemia and 3h of reperfusion were applied to the left kidneys of all rats (apart from SG) under 25 mg/kg thiopental sodium anesthesia. At the end of that time, kidneys were extracted and biochemical and immunohistochemical analyses were performed. Etoricoxib reduced, in a dose-dependent manner, levels of MDA, MPO and COX-2 that normally rise with I/R in rat kidney tissues. Etorixicob did not alter COX-1 activity at 50 and 100 mg/kg doses, but significantly prevented loss of tGSH in tissues with I/R. In addition, Bcl-2' gene expression inhibited with I/R was prevented in renal tubular and glomerular cells. Furthermore, etoricoxib significantly decreased the caspase-3 gene expression which increased with I/R. Etoricoxib significantly prevented I/R injury in a dose-dependent manner. The results of this study show that etoricoxib treatment could decrease kidney injury during IR.

Rosmarinic acid inhibits chemical hypoxia-induced cytotoxicity in primary cultured rat hepatocytes

We examine the effect of rosmarinic acid (RA) in chemical hypoxia-induced injury in rat hepatocytes. Cell viability was significantly decreased by cobalt chloride (CoCl2), a well-known hypoxia mimetic agent in a time- and dose- dependent manner. RA pretreatment before exposure to CoCl2 significantly attenuated the CoCl2-induced decrease of cell viability. Additionally, pretreatment with RA potentiated the decrease of Bcl-2 expression and attenuated the increase of Caspase-3 expression by CoCl2. CoCl2 treatment resulted in an increase of intracellular ROS generation, which is inhibited by RA or N-acetyl-cysteine (NAC, a ROS scavenger), and p38MAPK phosphorylation, which is also blocked by RA or NAC. CoCl2-induced increase of Bax/Bcl-2 ratio and Caspase-3 expression was attenuated by RA, NAC and SB203580 (p38MAPK inhibitor). CoCl2-induced decrease of cell viability was also attenuated by RA, NAC and SB203580 pretreatment. Additionally, RA inhibited CoCl2-induced COX-2 expression and prostaglandin E2 (PGE2) secretion. Similar to the effect of RA, both NAC and NS-398 (COX-2 inhibitor) blocked CoCl2-induced COX-2 expression and PGE2 secretion. NS-398 attenuated not only CoCl2-induced increase of Bax/Bcl-2 ratio and Caspase-3 expression, but decrease of cell viability. Taken together, RA protects primary cultured rat hepatocytes against CoCl2-induced cell injury through inhibition of ROS-activated p38MAPK and COX-2/PGE2 pathway.

Hepatic ischemia and reperfusion injury in the absence of myeloid cell-derived COX-2 in mice

Cyclooxygenase-2 (COX-2) is a mediator of hepatic ischemia and reperfusion injury (IRI). While both global COX-2 deletion and pharmacologic COX-2 inhibition ameliorate liver IRI, the clinical use of COX-2 inhibitors has been linked to increased risks of heart attack and stroke. Therefore, a better understanding of the role of COX-2 in different cell types may lead to improved therapeutic strategies for hepatic IRI. Macrophages of myeloid origin are currently considered to be important sources of the COX-2 in damaged livers. Here, we used a Cox-2^flox conditional knockout mouse (COX-2^−M/−M) to examine the function of COX-2 expression in myeloid cells during liver IRI. COX-2^−M/−M mice and their WT control littermates were subjected to partial liver ischemia followed by reperfusion. COX-2^−M/−M macrophages did not express COX-2 upon lipopolysaccharide stimulation and COX-2^−M/−M livers showed reduced levels of COX-2 protein post-IRI. Nevertheless, selective deletion of myeloid cell-derived COX-2 failed to ameliorate liver IRI; serum transaminases and histology were comparable in both COX-2^−M/−M and WT mice. COX-2^−M/−M livers, like WT livers, developed extensive necrosis, vascular congestion, leukocyte infiltration and matrix metalloproteinase-9 (MMP-9) expression post-reperfusion. In addition, myeloid COX-2 deletion led to a transient increase in IL-6 levels after hepatic reperfusion, when compared to controls. Administration of celecoxib, a selective COX-2 inhibitor, resulted in significantly improved liver function and histology in both COX-2^−M/−M and WT mice post-reperfusion, providing evidence that COX-2-mediated liver IRI is caused by COX-2 derived from a source(s) other than myeloid cells. In conclusion, these results support the view that myeloid COX-2, including myeloid-macrophage COX-2, is not responsible for the hepatic IRI phenotype.

Gene expression profiles in granuloma tissue reveal novel diagnostic markers in sarcoidosis

Sarcoidosis is an immune-mediated multisystem disease characterized by the formation of non-caseating granulomas. The pathogenesis of sarcoidosis is unclear, with proposed infectious or environmental antigens triggering an aberrant immune response in susceptible hosts. Multiple pro-inflammatory signaling pathways have been implicated in mediating macrophage activation and granuloma formation in sarcoidosis, including IFN-γ/STAT-1, IL-6/STAT-3, and NF-κB. It is difficult to distinguish sarcoidosis from other granulomatous diseases or assess disease severity and treatment response with histopathology alone. Therefore, development of improved diagnostic tools is imperative. Herein, we describe an efficient and reliable technique to classify granulomatous disease through selected gene expression and identify novel genes and cytokine pathways contributing to the pathogenesis of sarcoidosis. We quantified the expression of twenty selected mRNAs extracted from formalin-fixed paraffin embedded (FFPE) tissue (n = 38) of normal lung, suture granulomas, sarcoid granulomas, and fungal granulomas. Utilizing quantitative real-time RT-PCR we analyzed the expression of several genes, including IL-6, COX-2, MCP-1, IFN-γ, T-bet, IRF-1, Nox2, IL-33, and eotaxin-1 and revealed differential regulation between suture, sarcoidosis, and fungal granulomas. This is the first study demonstrating that quantification of target gene expression in FFPE tissue biopsies is a potentially effective diagnostic and research tool in sarcoidosis.

Leukocyte transmigration across endothelial and extracellular matrix protein barriers in liver ischemia/reperfusion injury

PURPOSE OF REVIEW

Hepatic ischemia reperfusion injury (IRI) linked to leukocyte recruitment and subsequent release of cytokines and free radicals remains a significant complication in organ transplantation. The aim of this review is to bring attention to advances made in our understanding of the mechanisms of leukocyte recruitment to sites of inflammatory stimulation in liver IRI.

RECENT FINDINGS

Leukocyte transmigration across endothelial and extracellular matrix barriers is dependent on adhesive events, as well as on focal matrix degradation mechanisms. Whereas adhesion molecules are critical for the successful promotion of leukocyte transmigration by providing leukocyte attachment to the vascular endothelium, matrix metalloproteinases (MMPs) are important for facilitating leukocyte movement across vascular barriers. Among different MMPs, MMP-9, an inducible gelatinase expressed by leukocytes during hepatic IRI, is emerging as an important mediator of leukocyte traffic to inflamed liver.

SUMMARY

It is generally accepted that the understanding of the molecular mechanisms involved in leukocyte recruitment will lead to the development of novel targeted therapeutic approaches for hepatic IRI and liver transplantation. Here, we review mechanisms of leukocyte traffic in liver IRI and the role of some of the proteins that are thought to be important for this process.

Atherosclerosis, dyslipidemia, and inflammation: the significant role of polyunsaturated Fatty acids

Phospholipids play an essential role in cell membrane structure and function. The length and number of double bonds of fatty acids in membrane phospholipids are main determinants of fluidity, transport systems, activity of membrane-bound enzymes, and susceptibility to lipid peroxidation. The fatty acid profile of serum lipids, especially the phospholipids, reflects the fatty acid composition of cell membranes. Moreover, long-chain n-3 polyunsatured fatty acids decrease very-low-density lipoprotein assembly and secretion reducing triacylglycerol production. N-6 and n-3 polyunsatured fatty acids are the precursors of signalling molecules, termed "eicosanoids," which play an important role in the regulation of inflammation. Eicosanoids derived from n-6 polyunsatured fatty acids have proinflammatory actions, while eicosanoids derived from n-3 polyunsatured fatty acids have anti-inflammatory ones. Previous studies showed that inflammation contributes to both the onset and progression of atherosclerosis: actually, atherosclerosis is predominantly a chronic low-grade inflammatory disease of the vessel wall. Several studies suggested the relationship between long-chain n-3 polyunsaturated fatty acids and inflammation, showing that fatty acids may decrease endothelial activation and affect eicosanoid metabolism.

Monoacylglycerol lipase controls endocannabinoid and eicosanoid signaling and hepatic injury in mice

BACKGROUND & AIMS

The endocannabinoid and eicosanoid lipid signaling pathways have important roles in inflammatory syndromes. Monoacylglycerol lipase (MAGL) links these pathways, hydrolyzing the endocannabinoid 2-arachidonoylglycerol to generate the arachidonic acid precursor pool for prostaglandin production. We investigated whether blocking MAGL protects against inflammation and damage from hepatic ischemia/reperfusion (I/R) and other insults.

METHODS

We analyzed the effects of hepatic I/R in mice given the selective MAGL inhibitor JZL184, in Mgll(-/-) mice, fatty acid amide hydrolase(-/-) mice, and in cannabinoid receptor type 1(-/-) (CB1-/-) and cannabinoid receptor type 2(-/-) (CB2-/-). Liver tissues were collected and analyzed, along with cultured hepatocytes and Kupffer cells. We measured endocannabinoids, eicosanoids, and markers of inflammation, oxidative stress, and cell death using molecular biology, biochemistry, and mass spectrometry analyses.

RESULTS

Wild-type mice given JZL184 and Mgll(-/-) mice were protected from hepatic I/R injury by a mechanism that involved increased endocannabinoid signaling via CB2 and reduced production of eicosanoids in the liver. JZL184 suppressed the inflammation and oxidative stress that mediate hepatic I/R injury. Hepatocytes were the major source of hepatic MAGL activity and endocannabinoid and eicosanoid production. JZL184 also protected from induction of liver injury by D-(+)-galactosamine and lipopolysaccharides or CCl4.

CONCLUSIONS

MAGL modulates hepatic injury via endocannabinoid and eicosanoid signaling; blockade of this pathway protects mice from liver injury. MAGL inhibitors might be developed to treat conditions that expose the liver to oxidative stress and inflammatory damage.

Pretreatment with paricalcitol attenuates inflammation in ischemia-reperfusion injury via the up-regulation of cyclooxygenase-2 and prostaglandin E2

BACKGROUND

The effect of paricalcitol on renal ischemia-reperfusion injury (IRI) has not been investigated. We examined whether paricalcitol is effective in preventing inflammation in a mouse model of IRI, and evaluated the cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) pathways as a protective mechanism of paricalcitol.

METHODS

Paricalcitol (0.3 μg/kg) was administered to male C57BL/6 mice 24 h before IRI. Bilateral kidneys were subjected to 23 min of ischemia, and mice were killed 72 h after IRI. The effects of paricalcitol on renal IRI were evaluated in terms of renal function, tubular necrosis, apoptotic cell death, inflammatory cell infiltration and inflammatory cytokines. The effects of paricalcitol on COX-2, PGE2 and its receptors were investigated.

RESULTS

Paricalcitol pretreatment improved renal function (decreased blood urea nitrogen and serum creatinine levels), tubular necrosis and apoptotic cell death in IRI-mice kidneys. The infiltration of inflammatory cells (T cells and macrophages), and the production of proinflammatory cytokines (RANTES, tumor necrosis factor-α, interleukin-1β and interferon-γ) were reduced in paricalcitol-treated mice with IRI. Paricalcitol up-regulated COX-2 expression, PGE2 synthesis and mRNA expression of receptor subtype EP4 in post-ischemic renal tissue. The cotreatment of a selective COX-2 inhibitor with paricalcitol restored functional injury and tubular necrosis in paricalcitol-treated mice with IRI.

CONCLUSIONS

Our study demonstrates that paricalcitol pretreatment prevents renal IRI via the inhibition of renal inflammation, and the up-regulation of COX-2 and PGE2 is one of the protective mechanisms of paricalcitol in renal IRI.

Regulation of T helper cell subsets by cyclooxygenases and their metabolites

Cyclooxygenases and their metabolites are important regulators of inflammatory responses and play critical roles in regulating the differentiation of T helper cell subsets in inflammatory diseases. In this review, we highlight new information on regulation of T helper cell subsets by cyclooxygenases and their metabolites. Prostanoids influence cytokine production by both antigen presenting cells and T cells to regulate the differentiation of naïve CD4(+) T cells to Th1, Th2 and Th17 cell phenotypes. Cyclooxygenases and PGE2 generally exacerbate Th2 and Th17 phenotypes, while suppressing Th1 differentiation. Thus, cycloxygenases may play a critical role in diseases that involve immune cell dysfunction. Targeting of cyclooxygenases and their eicosanoid products may represent a new approach for treatment of inflammatory diseases, tumors and autoimmune disorders.

Fibronectin-α4β1 interactions in hepatic cold ischemia and reperfusion injury: regulation of MMP-9 and MT1-MMP via the p38 MAPK pathway

Liver ischemia-reperfusion injury (IRI) remains a challenging problem in clinical settings. The expression of fibronectin (FN) by endothelial cells is a prominent feature of the hepatic response to injury. Here we investigate the effects of the connecting segment-1 (CS-1) peptide therapy, which blocks FN-α4β1 integrin leukocyte interactions, in a well-established model of 24-h cold liver IRI. CS-1 peptides significantly inhibited leukocyte recruitment and local release of proinflammatory mediators (COX-2, iNOS and TNF-α), ameliorating liver IRI and improving recipient survival rate. CS1 therapy inhibited the phosphorylation of p38 MAPK, a kinase linked to inflammatory processes. Moreover, in addition to downregulating the expression of matrix metalloproteinase-9 (MMP-9) in hepatic IRI, CS-1 peptide therapy depressed the expression of membrane type 1-matrix metalloproteinase (MT1-MMP/MMP-14) by macrophages, a membrane-tethered MMP important for focal matrix proteolysis. Inhibition of p38 MAPK activity, with its pharmacological antagonist SB203580, downregulated MMP-9 and MT1-MMP/MMP-14 expressions by FN-stimulated macrophages, suggesting that p38 MAPK kinase pathway controls FN-mediated inductions of MMP-9 and MT1-MMP/MMP-14. Hence, this study provides new insights on the role of FN in liver injury, which can potentially be applied to the development of new pharmacological strategies for the successful protection against hepatic IRI.

Flurbiprofen, a cyclooxygenase inhibitor, protects mice from hepatic ischemia/reperfusion injury by inhibiting GSK-3β signaling and mitochondrial permeability transition

Flurbiprofen acts as a nonselective inhibitor for cyclooxygenases (COX-1 and COX-2), but its impact on hepatic ischemia/reperfusion (I/R) injury remains unclear. Mice were randomized into sham, I/R and flurbiprofen (Flurb) groups. The hepatic artery and portal vein to the left and median liver lobes were occluded for 90 min and unclamped for reperfusion to establish a model of segmental (70%) warm hepatic ischemia. Pretreatment of animals with flurbiprofen prior to I/R insult significantly decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH), and prevented hepatocytes from I/R-induced apoptosis/necrosis. Moreover, flurbiprofen dramatically inhibited mitochondrial permeability transition (MPT) pore opening, and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that flurbiprofen markedly inhibited glycogen synthase kinase (GSK)-3β activity and increased phosphorylation of GSK-3β at Ser9, which, consequently, could modulate the adenine nucleotide translocase (ANT)-cyclophilin D (CyP-D) complex and the susceptibility to MPT induction. Therefore, administration of flurbiprofen prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through inhibition of MPT and inactivation of GSK-3β, and provides experimental evidence for clinical use of flurbiprofen to protect liver function in surgical settings in addition to its conventional use for pain relief.

IL-17A-producing NK cells were implicated in liver injury induced by ischemia and reperfusion

NK cells play a critical role in several types of liver injury. The aim of this study was to evaluate the role of NK cells in liver ischemia reperfusion injury (IRI) and the underlying mechanism. Male Rag1-/- mice and wild type mice were subjected to partial hepatic IRI. Anti-NK1.1 (300 μg/mouse, ip) was used to deplete NK cells. Liver injury was evaluated by level of serum alanine aminotransferase (ALT). Hepatic inflammatory cytokines, neutrophils and CXCL-2 expression were measured following ischemia and reperfusion. Additionally, NK cells were cultured with or without IL-6, IL-21, IL-23 and IL-10 for 24h, then IL-17A level in the supernatants was analyzed by ELISA. Production of IL-17A was increased in NK cells after reperfusion. Various cytokines such as, IL-6, IL-21 and IL-23, which also elevated after IRI, can promote IL-17A production and up-regulate the phosphorylation of STAT3 in NK cells, while the increase was repressed in the presence of IL-10. Depletion of NK cells decreased IL-17A level in Rag1-/- mice ischemic lobes. Meanwhile, hepatic infiltration of neutrophils and CXCL-2 level were reduced and liver injury was ameliorated. Neutralization of IL-17A was used to confirm the role of this cytokine produced by NK cells in Rag1-/- mice. In conclusion, at initial stage of liver IRI, NK cells increase IL-17A production and promote liver injury.

Cannabidiol protects against hepatic ischemia/reperfusion injury by attenuating inflammatory signaling and response, oxidative/nitrative stress, and cell death

Ischemia/reperfusion (I/R) is a pivotal mechanism of liver damage after liver transplantation or hepatic surgery. We have investigated the effects of cannabidiol (CBD), the nonpsychotropic constituent of marijuana, in a mouse model of hepatic I/R injury. I/R triggered time-dependent increases/changes in markers of liver injury (serum transaminases), hepatic oxidative/nitrative stress (4-hydroxy-2-nonenal, nitrotyrosine content/staining, and gp91phox and inducible nitric oxide synthase mRNA), mitochondrial dysfunction (decreased complex I activity), inflammation (tumor necrosis factor α (TNF-α), cyclooxygenase 2, macrophage inflammatory protein-1α/2, intercellular adhesion molecule 1 mRNA levels; tissue neutrophil infiltration; nuclear factor κB (NF-κB) activation), stress signaling (p38MAPK and JNK), and cell death (DNA fragmentation, PARP activity, and TUNEL). CBD significantly reduced the extent of liver inflammation, oxidative/nitrative stress, and cell death and also attenuated the bacterial endotoxin-triggered NF-κB activation and TNF-α production in isolated Kupffer cells, likewise the adhesion molecule expression in primary human liver sinusoidal endothelial cells stimulated with TNF-α and attachment of human neutrophils to the activated endothelium. These protective effects were preserved in CB2 knockout mice and were not prevented by CB1/2 antagonists in vitro. Thus, CBD may represent a novel, protective strategy against I/R injury by attenuating key inflammatory pathways and oxidative/nitrative tissue injury, independent of classical CB1/2 receptors.

Liver ischemia/reperfusion injury: processes in inflammatory networks--a review

Liver ischemia/reperfusion (IR) injury is typified by an inflammatory response. Understanding the cellular and molecular events underpinning this inflammation is fundamental to developing therapeutic strategies. Great strides have been made in this respect recently. Liver IR involves a complex web of interactions between the various cellular and humoral contributors to the inflammatory response. Kupffer cells, CD4+ lymphocytes, neutrophils, and hepatocytes are central cellular players. Various cytokines, chemokines, and complement proteins form the communication system between the cellular components. The contribution of the danger-associated molecular patterns and pattern recognition receptors to the pathophysiology of liver IR injury are slowly being elucidated. Our knowledge on the role of mitochondria in generating reactive oxygen and nitrogen species, in contributing to ionic disturbances, and in initiating the mitochondrial permeability transition with subsequent cellular death in liver IR injury is continuously being expanded. Here, we discuss recent findings pertaining to the aforementioned factors of liver IR, and we highlight areas with gaps in our knowledge, necessitating further research.

N-3 vs. saturated fatty acids: effects on the arterial wall

Cardiovascular disease is a leading cause of death worldwide. Atherosclerosis and unstable plaques are underlying causes for cardiovascular diseases. Cardiovascular disease is associated with consumption of diets high in saturated fats. In contrast there is increasing evidence that higher intakes of dietary n-3 fatty acids decrease risk for cardiovascular disease. Recent studies are beginning to clarify how n-3 compared with saturated fatty acids influence cardiovascular disease risk via pathways in the arterial wall. In this paper we will review studies that report on mechanisms whereby dietary fatty acids affect atherosclerosis through modulation of arterial wall lipid deposition, inflammation, cell proliferation, and plaque vulnerability.