Resolvin D1 activates the sphingosine-1-phosphate signaling pathway in murine livers with ischemia/reperfusion injury.

Resolvins (Rvs) are endogenous lipid mediators that promote resolution of inflammation and return to homeostasis. We previously reported that RvD1 both facilitates M2 macrophage polarization of Kupffer cells (KCs) and efferocytosis and modulates thioredoxin 2-mediated mitochondrial quality control in liver ischemia/reperfusion (IR) injury. However, the specific cellular or molecular targets of RvD1 remain poorly understood. Sphingosine-1-phosphate (S1P), the natural sphingolipid ligand for a family of G protein-coupled receptors (S1P1-S1P5), regulates lymphocyte circulation and various immune responses. Here we investigated the role of RvD1 in IR-induced hepatocellular damage with a focus on S1P signaling. Male C57BL/6 mice were subjected to partial hepatic ischemia for 60 min, followed by reperfusion. Mice were pretreated with RvD1 (15 µg/kg, i.p.) 1 h prior to ischemia and immediately before reperfusion. To deplete KCs, liposome clodronate was administered (100 µL/mice, i.v.) 24 h prior to ischemia. Mice were pretreated with VPC23019 (100 µg/kg, i.p.), an antagonist for S1P1/S1P3 10 min prior to initial RvD1 treatment. Exogenous RvD1 attenuated IR-induced hepatocellular damage as evidenced by serum HMGB1 release. RvD1 attenuated the decrease in hepatic S1P concentration induced by IR. KC depletion by liposome clodronate did not alter the effect of RvD1 on sphingosine kinases (SKs) and S1P receptors, suggesting independency of KCs. Moreover, in purified hepatocytes of mice exposed to IR, mRNA expression of SK1, SK2, S1P1, and S1P3 decreased significantly, and this was attenuated by RvD1. Finally, VPC23019 pretreatment abolished the hepatoprotective effects of RvD1 in serum HMGB1 release. Our findings suggest that RvD1 protects the liver against IR injury by activating S1P signaling.

Pterostilbene protects against acetaminophen-induced liver injury by restoring impaired autophagic flux.

An overdose of acetaminophen (APAP) causes liver injury through formation of N-acetyl-p-benzoquinoneimine, which overproduces reactive oxygen species (ROS). Autophagy maintains cellular homeostasis and is regulated by generation of ROS. Pterostilbene (PTE) has been shown to have antioxidant and anti-inflammatory properties. In this study, we investigated the protective mechanisms of PTE against APAP-induced liver injury, focusing on autophagy. ICR mice were intraperitoneally (i.p.) treated with 400 mg/kg of APAP. PTE (15, 30, and 60 mg/kg, i.p.) and chloroquine (CQ, 60 mg/kg, i.p.) were injected 1 h after APAP treatment. Blood and liver tissues were isolated 6 h after APAP treatment. PTE decreased serum aminotransferase activities and hepatic oxidative stress; this protective effect was abolished by CQ. APAP impaired autophagic flux, as evidenced by increased microtubule-associated protein-1 light chain 3-II and p62 protein expression; this impaired autophagic flux was restored by PTE, while CQ abolished this effect. APAP decreased beclin-1 and autophagy related protein 7 protein expressions, while PTE attenuated these decreases. PTE increased the lysosome-associated membrane protein-2 protein expression and decreased the mammalian target of rapamycin and Unc-51 like autophagy activating kinase 1 phosphorylation. Our findings suggest that PTE protects against APAP-induced hepatotoxicity by enhancing autophagic flux.

Intracellular transformation rates of fatty acids are influenced by expression of the fatty acid transporter FadL in Escherichia coli cell membrane.

Fatty acids have a low permeability through the cell membrane. Therefore, the intracellular biotransformation of fatty acids can be slow due to supply limitations. The effects of expression level of the fatty acid transporter FadL in Escherichia coli on the biotransformations were investigated. The enhanced expression of FadL led to 5.5-fold increase of the maximum reaction rate Vmax (i.e., 200 µmol/min per g dry cells (200 U/g dry cells)) of the recombinant E. coli expressing a hydratase of Stenotrophomonas maltophilia in the periplasm with respect to hydration of oleic acid. The FadL expression level was also critical for oxidation of 12- and 10- hydroxyoctadecanoic acid by the recombinant E. coli expressing an alcohol dehydrogenase (ADH) of Micrococcus luteus. In addition, the multistep biotransformation of ricinoleic acid into the ester (i.e., (Z)-11-(heptanoyloxy)undec-9-enoic acid) by the recombinant E. coli expressing the ADH of M. luteus and a Baeyer-Villiger monooxygenase of Pseudomonas putida KT2440 was 2-fold increased to 40 U/g dry cells with expression of FadL to an appropriate level. The FadL expression level is one of the critical factors to determine whole-cell biotransformation rates of not only long chain fatty acids but also hydroxy fatty acids. This study may contribute to whole-cell biocatalyst engineering for biotransformation of hydrophobic substances.

Effects of Zanthoxylum piperitum ethanol extract on osteoarthritis inflammation and pain.

Degenerative arthritis, also known as osteoarthritis (OA), is the most common type of arthritis, which is caused by degenerative damage of the cartilage, which primarily protects the joints, leading to inflammation and pain. The objective of this study was to investigate the in vivo and in vitro effects of treatment with ZPE-LR (90% EtOH extract of Zanthoxylum piperitum) on pain severity and inflammation. When using an in vivo OA model MIA (monosodiumidoacetate-induced arthritis) rats, ZPE-LR (100 mg/kg) oral-administratio significantly inhibited MIA-induced change in loaded weight ratio on the left foot, and articular cartilage thickness. To confirm the positive effects on pain relief, acetic acid, heat and formalin-induced pain were remarkably decreased by 50 and 100 mg/kg ZPE-LR oral-administration. Pain related KCNJ6 mRNA expression as well as K + current was increased after ZPE-LR treatment in BV-2 cells. To confirm the positive effects on inflammation, TPA (12-O-tetradecanoylphorbol-13-acetate) induced inflammation measured by mouse ear thickness and biopsy punch weight and TPA-induced iNOS, COX-2 mRNA and protein expression were remarkably suppressed by 50 and 100 mg/kg ZPE-LR oral-administration. In addition, TPA-induced iNOS, COX-2 mRNA level and protein expression were reduced. Acetic acid, heat and formalin-induced pain were remarkably decreased by 50 and 100 mg/kg ZPE-LR oral-administration. We examined in vitro ZPE-LR effects in LPS-induced RAW 264.7 cells. LPS-induced p65 translocation to the nucleus was prohibited by ZPE-LR 100 µg/ml oral administration. Moreover, ROS generation by LPS was significantly inhibited by ZPE-LR 50 and 100 µg/ml treatment. To investigate new ZPE-LR activating mechanisms, the gene fishing method (not a typical term, should probably use PCR based genetic screening) was used. LPS-induced HPRT1 (hypoxanthine phosphoribosyltransferase 1) was decreased by ZPE-LR. However, RPL8 (Ribosomal protein L8) which showed no change in mRNA expression due to LPS, did show increased mRNA levels after ZPE-LR treatment. Our data elucidate mechanisms underlying ZPE-LR and suggest ZPE-LR may be a potential therapeutic agent to modulate osteoarthritis inflammation and pain.

BST106 Protects against Cartilage Damage by Inhibition of Apoptosis and Enhancement of Autophagy in Osteoarthritic Rats.

Chrysanthemum zawadskii var. latilobum (CZ) has been used as a traditional medicine in Asian countries for the treatment of inflammatory diseases. Recently, CZ extract was shown to inhibit differentiation of osteoclasts and provide protection against rheumatoid arthritis. The aim of this study was to investigate the molecular mechanisms of BST106, the ethanol extract of CZ, for cartilage protection in monosodium iodoacetate (MIA)-induced osteoarthritis (OA), particularly focusing on apoptosis and autophagy. BST106 (50, 100, and 200 mg/kg) was orally administered once daily to MIA-induced OA rats. Swelling, limping, roentgenography, and histomorphological changes were assessed 28 d after MIA injection. Biochemical parameters for matrix metalloproteinase (MMP), apoptosis, and autophagy were also assessed. BST106 ameliorated the severity of swelling and limping after MIA injection. Roentgenographic and histomorphological examinations revealed that BST106 reduced MIA-induced cartilage damage. BST106 decreased MIA-induced increases in MMP-2 and MMP-13 mRNA levels. Increased levels of serum cartilage oligomeric matrix protein and glycosaminoglycan release were attenuated by BST106. Furthermore, BST106 suppressed the protein expression of proapoptotic molecules and increased the protein expression of autophagosome- and autolysosome-related molecules. These findings indicate that BST106 protects against OA-induced cartilage damage by inhibition of the apoptotic pathway and restoration of impaired autophagic flux.

Resolvin D1 attenuates liver ischaemia/reperfusion injury through modulating thioredoxin 2-mediated mitochondrial quality control.

BACKGROUND AND PURPOSE: Liver ischaemia and reperfusion (IR) injury is a sterile inflammatory response involving production of ROS. Mitochondrial homeostasis is maintained by mitochondrial quality control (QC). Thioredoxin (TRX) 2 is a key mitochondrial redox-sensitive protein. Resolvin D1 (RvD1), a specialized pro-resolving lipid mediator, exerts anti-inflammatory and antioxidant activities. We investigated mechanisms of RvD1 protection against IR-induced oxidative damage to the liver, focusing on TRX2-mediated mitochondrial QC. EXPERIMENTAL APPROACH: Mice underwent partial warm IR. RvD1 was administered 1 h before ischaemia and immediately prior to reperfusion. Human liver carcinoma HepG2 cells were exposed to hypoxia/reoxygenation and transfected with TRX2 siRNA. Immunohistochemistry, Western blotting and enzyme assays were used to follow changes in mitochondrial structure and function. KEY RESULTS: RvD1 attenuated hepatocellular damage following IR, assessed by serum aminotransferase activities and histology. RvD1 reduced mitochondrial swelling, lipid peroxidation and glutamate dehydrogenase release. Impaired activities of mitochondrial complexes I and III were restored by RvD1. RvD1 enhanced expression of the mitophagy-related protein, Parkin and inhibited accumulation of PTEN-induced putative kinase 1. RvD1 restored levels of mitochondrial biogenesis proteins including PPARγ coactivator 1α, nuclear respiratory factor 1 and mitochondrial transcription factor A and mtDNA level. RvD1 attenuated the increase in levels of the mitochondrial fission-related protein, dynamin-related protein 1. IR reduced TRX2 levels while increasing TRX2 association with TRX-interacting protein. RvD1 attenuated these changes. The regulatory effects of RvD1 on mitochondrial QC were abolished by TRX2 knockdown. CONCLUSIONS AND IMPLICATIONS: We suggest that RvD1 ameliorated IR-induced hepatocellular damage by regulating TRX2-mediated mitochondrial QC.

Heme oxygenase-1 protects liver against ischemia/reperfusion injury via phosphoglycerate mutase family member 5-mediated mitochondrial quality control.

AIMS: Heme oxygenase-1 (HO-1), an endogenous cytoprotective enzyme, is reported that can be localized in mitochondria under stress, contributing to preserve mitochondrial function. Mitochondrial quality control (QC) is essential to cellular health and recovery linked with redox homeostasis. Recent studies reported that phosphoglycerate mutase family member (PGAM) 5, a mitochondria-resident phosphatase, plays critical role in mitochondrial homeostasis. Therefore, we aim to investigate cytoprotective mechanisms of HO-1 in I/R-induced hepatic injury focusing on mitochondrial QC associated with PGAM5 signaling. MAIN METHODS: Mice were subjected to 60 min of hepatic ischemia followed by 6 h reperfusion and were pretreated twice with hemin (HO-1 inducer, 30 mg/kg) or zinc protoporphyrin (ZnPP; HO-1 inhibitor, 10 mg/kg) 16 and 3 h before ischemia. KEY FINDINGS: I/R increased hepatic and mitochondrial HO activity, which was augmented by hemin. I/R-induced hepatocellular and mitochondrial damages were attenuated by hemin and augmented by ZnPP. Meanwhile, I/R increased mitochondrial biogenesis, as evidenced by increased mitochondrial DNA contents and mitochondrial transcription factor A protein expression. Hemin augmented these results. I/R impaired mitophagy, as indicated by decreases in Parkin protein expression and the number of mitophagic vacuoles. These changes were attenuated by hemin. Hemin attenuated the I/R-induced increase in mitochondrial fission-related protein, dynamin-related protein 1, and the decrease in PGAM5 protein expression. Furthermore, PGAM5 siRNA abolished the effect of HO-1 on mitochondrial QC in HepG2 cells subjected to hypoxia/reoxygenation. SIGNIFICANCE: Our findings suggest that HO-1 protects against I/R-induced hepatic injury via regulation of mitochondrial QC by PGAM5 signaling.

Heme Oxygenase-1 Protects the Liver from Septic Injury by Modulating TLR4-Mediated Mitochondrial Quality Control in Mice.

Mitochondrial dysfunction is involved in the pathogenesis of sepsis-induced multiple organ dysfunction syndrome (MODS). Mitochondrial quality control (QC) is characterized by self-recovering mitochondrial damage through mitochondrial biogenesis, mitophagy, and fission/fusion. Heme oxygenase (HO)-1 acts as a signaling molecule to modulate inflammation. The present study elucidated the cytoprotective mechanisms of HO-1 in sepsis, particularly focusing on toll-like receptor (TLR)4-mediated mitochondrial QC. Mice were subjected to sepsis by cecal ligation and puncture (CLP). The mice were injected intraperitoneally with hemin (10 mg/kg) at 12 h before CLP or zinc protoporphyrin IX (ZnPP; 30 mg/kg) at 2 h before CLP. The serum and tissues were collected 6 h after CLP. Mortality, MODS, and proinflammatory cytokines increased in septic mice. These increases were augmented by ZnPP but attenuated by hemin. Hemin decreased mitochondrial lipid peroxidation and mitochondrial dysfunction. Hemin enhanced mitochondrial biogenesis, as indicated by increased levels of peroxisome proliferator-activated receptor-γ coactivator 1α, nuclear respiratory factor 1, and mitochondrial transcription factor A (TFAM). Hemin also enhanced mitophagy, as indicated by decreased PTEN-induced putative kinase 1 (PINK1) level and increased Parkin level. Hemin decreased fission-related protein, dynamin-related protein 1 (DRP1), and increased fusion-related protein, mitofusin 2. Hemin attenuated the increased TLR4 expression. TAK-242, a TLR4 antagonist, attenuated mortality, inflammatory response, and impaired mitochondrial QC. Our findings suggest that HO-1 attenuates septic injury by modulating TLR4-mediated mitochondrial QC.

Necrostatin-1 Protects Against D-Galactosamine and Lipopolysaccharide-Induced Hepatic Injury by Preventing TLR4 and RAGE Signaling.

Fulminant hepatic failure (FHF) is a life-threatening clinical syndrome results in massive inflammation and hepatocyte death. Necroptosis is a regulated form of necrotic cell death that is emerging as a crucial control point for inflammatory diseases. The kinases receptor interacting protein (RIP) 1 and RIP3 are known as key modulators of necroptosis. In this study, we investigated the impact of necroptosis in the pathogenesis of FHF and molecular mechanisms, particularly its linkage to damage-associated molecular pattern (DAMP)-mediated pattern recognition receptor (PRR) signaling pathways. Male C57BL/6 mice were given an intraperitoneal injection of necrostatin-1 (Nec-1, RIP1 inhibitor; 1.8 mg/kg; dissolved in 2% dimethyl sulfoxide in phosphate-buffered saline) 1 h before receiving D-galactosamine (GalN; 800 mg/kg)/lipopolysaccharide (LPS; 40 µg/kg). Hepatic RIP1, RIP3 protein expression, their phosphorylation, and RIP1/RIP3 complex formation upregulated in the GalN/LPS group were attenuated by Nec-1. Nec-1 markedly reduced the increases in mortality and serum alanine aminotransferase activity induced by GalN/LPS. Increased serum high mobility group box 1 (HMGB1) and interleukin (IL)-33 release, HMGB1-toll-like receptor 4 and HMGB1-receptor for advanced glycation end products (RAGE) interaction, and nuclear protein expressions of NF-κB and early growth response protein-1 (egr-1) were attenuated by Nec-1. Our finding suggests that necroptosis is responsible for GalN/LPS-induced liver injury through DAMP-activated PRR signaling.

Genipin protects d-galactosamine and lipopolysaccharide-induced hepatic injury through suppression of the necroptosis-mediated inflammasome signaling.

Acute liver failure (ALF) is a life-threatening syndrome resulting from massive inflammation and hepatocyte death. Necroptosis, a programmed cell death controlled by receptor-interacting protein kinase (RIP) 1 and RIP3, has been shown to play an important role in regulating inflammation via crosstalk between other intracellular signaling. The inflammasome is a major intracellular multiprotein that induces inflammatory responses by mediating immune cell infiltration, thus potentiating injury. Genipin, a major active compound of the gardenia fruit, exhibits anti-inflammatory, antioxidant, and anti-apoptotic properties. This study investigated the hepatoprotective mechanisms of genipin on d-galactosamine (GalN) and lipopolysaccharide (LPS)-induced ALF, particularly focusing on interaction between necroptosis and inflammasome. Mice were given an intraperitoneal injection of genipin (25, 50, and 100mg/kg) or necrostatin-1 (Nec-1, a necroptosis inhibitor; 1.8mg/kg) 1h prior to GalN (800mg/kg)/LPS (40µg/kg) injection and were killed 3h after GalN/LPS injection. Genipin improved the survival rate and attenuated increases in serum aminotransferase activities and inflammatory cytokines after GalN/LPS injection. Genipin reduced GalN/LPS-induced increases in RIP3, phosphorylated RIP1 and RIP3 protein expression, and RIP1/RIP3 necrosome complex, similar to the effects of Nec-1. GalN/LPS significantly increased serum levels of high-mobility group box 1 and interleukin (IL)-33, which were attenuated by genipin and Nec-1. Moreover, similar to Nec-1, genipin attenuated GalN/LPS-induced increases in the protein expression levels of NLRP3, ASC, and caspase-1, inflammasome components, and levels of liver and serum IL-1ß. Taken together, our findings suggest that genipin ameliorates GalN/LPS-induced hepatocellular damage by suppressing necroptosis-mediated inflammasome signaling.

Genipin protects the liver from ischemia/reperfusion injury by modulating mitochondrial quality control.

Hepatic ischemia and reperfusion (IR) injury is closely linked to oxidative mitochondrial damage. Since mitochondrial quality control (QC) plays a pivotal role in the recovery of impaired mitochondrial function, mitochondrial QC has emerged as a potential therapeutic target. Genipin, an iridoid compound from Gardenia jasminoides, has been showed antioxidant and anti-inflammatory properties. In this study, we investigated the hepatoprotective mechanism of genipin against IR-induced hepatic injury, particularly focusing on mitochondrial QC. Male C57BL/6 mice underwent liver ischemia for 60min, followed by reperfusion for 6h. Genipin (100mg/kg, i.p.) or vehicle (10% Tween 80 in saline) was administrated to mice 1h before ischemia. Liver and blood samples were collected 6h after reperfusion. Hepatic IR increased hepatocellular oxidative damage and induced mitochondrial dysfunction. These phenomena were ameliorated by genipin. Hepatic IR also increased the level of mitochondrial fission, such as dynamin-related protein 1 and the level of PINK1 protein expression. In contrast, hepatic IR decreased the levels of mitochondrial biogenesis related proteins (e.g., peroxisome proliferator-activated receptor gamma coactivator 1α, nuclear respiratory factor 1, and mitochondrial transcription factor A), mitophagy related proteins (e.g., Parkin), and fusion related protein (e.g., mitofusin 2). Furthermore, hepatic IR decreased the levels of sirtuin1 protein and phosphorylation of AMP-activated protein kinase. Genipin alleviated these IR-induced changes. These data indicate that genipin protects against IR-induced hepatic injury via regulating mitochondrial QC. (225/250).

Overexpression of HO-1 Contributes to Sepsis-Induced Immunosuppression by Modulating the Th1/Th2 Balance and Regulatory T-Cell Function.

Background: Countervailing anti-inflammatory response and immunosuppression can cause death in late sepsis. Depletion and dysfunction of T cells are critical for developing sepsis-induced immunosuppression. Heme oxygenase-1 (HO-1) has a regulatory effect on differentiation and function of T cells and anti-inflammatory properties. We therefore investigated the immunosuppressive role of HO-1 in sepsis with a focus on its effects on helper T-cell (Th) differentiation and regulatory T cells (Treg). Methods: Sepsis was induced by cecal ligation and puncture (CLP). Mice were intraperitoneally injected with zinc protoporphyrin (ZnPP; 25 mg/kg), an HO-1 inhibitor, or hemin (20 mg/kg), an HO-1 inducer, at 24 and 36 hours post-CLP. Splenocytes were isolated 48 hours post-CLP. Mice were intranasally infected with Pseudomonas aeruginosa 4 days post-CLP as a secondary pneumonia infection model. Results: ZnPP improved survival and bacterial clearance, whereas hemin had the opposite effect in septic mice. CLP induced lymphocyte apoptosis and a proinflammatory Th1 to anti-inflammatory Th2 shift, which was attenuated by ZnPP. ZnPP attenuated the CLP-induced Treg population and protein expression of inhibitory costimulatory molecules. Furthermore, ZnPP improved survival in the secondary pneumonia infection model. Conclusions: Our findings suggest that HO-1 overexpression contributes to sepsis-induced immunosuppression during late phase sepsis by promoting Th2 polarization and Treg function.

2-Methoxyestradiol protects against ischemia/reperfusion injury in alcoholic fatty liver by enhancing sirtuin 1-mediated autophagy.

Alcoholic fatty liver (AFL) is susceptible to ischemia/reperfusion (I/R) injury, responding with inflammation and extensive hepatocellular damage. Autophagy maintains cellular homeostasis and regulates inflammation and lipid metabolism. 2-Methoxyestradiol (2-ME2), an endogenous metabolite of estradiol, exhibits antioxidant and anti-inflammatory properties. This study examined the cytoprotective mechanisms of 2-ME2 on hepatic I/R in AFL, focusing on autophagy signaling. C57BL/6 mice were fed an ethanol diet (ED) to induce AFL, or a control diet (CD) for 6weeks, and then subjected to 60min of ischemia and 5h of reperfusion. 2-ME2 (15mg/kg, i.p.) was administered 12h before ischemia and 10min before reperfusion, and sirtinol (sirtuin 1 (SIRT1) inhibitor, 10mg/kg, i.p.) was administered 30min before reperfusion. After reperfusion, ED animals showed higher serum aminotransferase activities and proinflammatory cytokine levels, and more severe histological changes compared with CD animals. These alterations were attenuated by 2-ME2. In the ED I/R group, autophagy and mitophagy were significantly impaired, as indicated by decreased hepatic levels of microtubule-associated protein 1 light chain 3 II and parkin protein expression, and increased p62 protein expression, which were attenuated by 2-ME2. The hepatic levels of Atg12-5 complex, Atg3, Atg7, lysosomal-associated membrane protein 2 and Rab7 protein expression significantly decreased in ED I/R animals, which were attenuated by 2-ME2. In the ED I/R group, the level of SIRT1 protein expression and its catalytic activity significantly decreased, which were attenuated by 2-ME2. Sirtinol reversed the stimulatory effect of 2-ME2 on autophagy. Our findings suggest that 2-ME2 ameliorates I/R-induced hepatocellular damage in AFL through activating SIRT1-mediated autophagy signaling.

Afzelin ameliorates D-galactosamine and lipopolysaccharide-induced fulminant hepatic failure by modulating mitochondrial quality control and dynamics.

BACKGROUND AND PURPOSE: Fulminant hepatic failure (FHF) is a fatal clinical syndrome that results in excessive inflammation and hepatocyte death. Mitochondrial dysfunction is considered to be a possible mechanism of FHF. Afzelin, a flavonol glycoside found in Houttuynia cordata Thunberg, has anti-inflammatory and antioxidant properties. The present study elucidated the cytoprotective mechanisms of afzelin against D-galactosamine (GalN)/LPS induced FHF, particularly focusing on mitochondrial quality control and dynamics. EXPERIMENTAL APPROACH: Mice were administered afzelin i.p. 1 h before receiving GalN (800 mg·kg-1 )/LPS (40 µg·kg-1 ), and they were then killed 5 h after GalN/LPS treatment. KEY RESULTS: Afzelin improved the survival rate and reduced the serum levels of alanine aminotransferase and pro-inflammatory cytokines in GalN/LPS-treated mice. Afzelin attenuated the mitochondrial damage, as indicated by diminished mitochondrial swelling and mitochondrial glutamate dehydrogenase activity in GalN/LPS-treated mice. Afzelin enhanced mitochondrial biogenesis, as indicated by increased levels of PPAR-γ coactivator 1α, nuclear respiratory factor 1 and mitochondrial transcription factor A. Afzelin also decreased the level of mitophagy-related proteins, parkin and PTEN-induced putative kinase 1. Furthermore, while GalN/LPS significantly increased the level of fission-related protein, dynamin-related protein 1, and decreased the level of fusion-related protein, mitofusin 2; these effects were attenuated by afzelin. CONCLUSIONS AND IMPLICATIONS: Our findings demonstrated that afzelin protects against GalN/LPS-induced liver injury by enhancing mitochondrial biogenesis, suppressing excessive mitophagy and balancing mitochondrial dynamics.

Role of necroptosis in autophagy signaling during hepatic ischemia and reperfusion.

Ischemia and reperfusion (I/R) is a complex phenomenon involving massive inflammation and cell death. Necroptosis refers to a newly described cell death as "programmed necrosis" that is controlled by receptor-interacting protein kinase (RIP) 1 and RIP3, which is involved in the pathogenesis of several inflammatory diseases. Autophagy is an essential cytoprotective system that is rapidly activated in response to various stimuli and involves crosstalk between different modes of cell death and inflammation. In this study, we investigated pattern changes in necroptosis and its role in autophagy signaling during hepatic I/R. Male C57BL/6 mice were subjected to 60min of ischemia followed by 3h reperfusion. Necrostatin-1 (Nec-1, a necroptosis inhibitor; 1.65mg/kg) was administered intraperitoneally 5min before reperfusion. Hepatic I/R significantly increased the level of RIP3, phosphorylated RIP1 and RIP3 protein expression, and RIP1/RIP3 necrosome formation, which were attenuated by Nec-1. I/R also significantly increased serum levels of alanine aminotransferase, tumor necrosis factor-α, and interleukin-6, which were attenuated by Nec-1. Meanwhile, hepatic I/R activated autophagy and mitophagy, as evidenced by increased LC3-II, PINK1, and Parkin, and decreased sequestosome 1/p62 protein expression. Nec-1 attenuated these changes and attenuated the increased levels of autophagy-related protein (ATG) 3, ATG7, Rab7, and cathepsin B protein expression during hepatic I/R. Moreover, hepatic I/R activated the extracellular signal-regulated kinase (ERK) pathway, and Nec-1 attenuated this increase. Taken together, our findings suggest that necroptosis contributes to hepatic damage during I/R, which induces autophagy via ERK activation.

Enhanced nitric oxide-mediated autophagy contributes to the hepatoprotective effects of ischemic preconditioning during ischemia and reperfusion.

Ischemic preconditioning (IPC) protects against liver ischemia/reperfusion (I/R) injury. Autophagy is an essential cytoprotective system that is rapidly activated by multiple stressors. Nitric oxide (NO) acts as an inducer of IPC. We examined the impact of autophagy in liver IPC and its regulation by NO. Male C57BL/6 mice were subjected to 60 min of hepatic ischemia followed by 6 h of reperfusion. IPC was achieved for 10 min of ischemia followed by 10 min of reperfusion prior to sustained ischemia. N(ω)-Nitro-l-arginine methyl ester (L-NAME, 15 mg/kg, i.v., all NOS inhibitor) and aminoguanidine (AG, 10 mg/kg, i.v., iNOS inhibitor) were injected 10 min before IPC. SB203580 (10 mg/kg, i.p., p38 inhibitor) was injected 30 min before IPC. I/R increased serum alanine aminotransferase activity. IPC attenuated this increase, which was abolished by L-NAME, but not AG. Microtubule-associated protein-1 light chain 3-II levels increased and p62 protein levels decreased after I/R; these changes were augmented by IPC and abolished by L-NAME. I/R increased liver protein expression of autophagy-related protein (Atg)12-Atg5 complex and lysosome-associated membrane protein-2. IPC augmented the expression of these proteins, which were abolished by L-NAME, but not AG. IPC also augmented the level of phosphorylated p38 MAPK induced by I/R and this phosphorylation was abolished by L-NAME. Our findings suggest that IPC-mediated NO protects against I/R-induced liver injury by enhancing autophagic flux.

Resolvin D1 protects the liver from ischemia/reperfusion injury by enhancing M2 macrophage polarization and efferocytosis.

Resolution of inflammation is an active process involving a novel category of lipid factors known as specialized pro-resolving lipid mediators, which includes Resolvin D1 (RvD1). While accumulating evidence suggests that RvD1 counteracts proinflammatory signaling and promotes resolution, the specific cellular targets and mechanisms of action of RvD1 remain largely unknown. In the present study, we investigated the role and molecular mechanisms of RvD1 in ischemia/reperfusion (IR)-induced sterile liver inflammation. Male C57BL/6 mice underwent 70% hepatic ischemia for 60min, followed by reperfusion. RvD1 (5, 10, and 15µg/kg, i.p.) was administered to the mice 1h before ischemia and then immediately prior to reperfusion. RvD1 attenuated IR-induced hepatocellular damage and the proinflammatory response. In purified Kupffer cells (KCs) from mice exposed to IR, the levels of M1 marker genes (Nos2a and Cd40) increased, while those of M2 marker genes (Arg1, Cd206, and Mst1r) decreased, demonstrating a proinflammatory shift. RvD1 markedly attenuated these changes. Depletion of KCs by liposome clodronate abrogated the effects of RvD1 on proinflammatory mediators and macrophage polarization. In addition, RvD1 attenuated increases in myeloperoxidase activity and Cxcl1 and Cxcl2 mRNA expression. RvD1 markedly augmented the efferocytic activity of KCs, as indicated by increases in F4/80(+)Gr-1(+) cells in the liver. However, antagonist pretreatment or gene silencing of the RvD1 receptor, ALX/FPR2, abrogated the anti-inflammatory and pro-resolving actions of RvD1. These data indicate that RvD1 ameliorates IR-induced liver injury, and this protection is associated with enhancement of M2 polarization and efferocytosis via ALX/FPR2 activation.

Pharmacological profiles of gemigliptin (LC15-0444), a novel dipeptidyl peptidase-4 inhibitor, in vitro and in vivo.

Gemigliptin, a novel dipeptidyl peptidase (DPP)-4 inhibitor, is approved for use as a monotherapy or in combination therapy to treat hyperglycemia in patients with type 2 diabetes mellitus. In this study, we investigated the pharmacological profiles of gemigliptin in vitro and in vivo and compared them to those of the other DPP-4 inhibitors. Gemigliptin was a reversible and competitive inhibitor with a Ki value of 7.25±0.67nM. Similar potency was shown in plasma from humans, rats, dogs, and monkeys. The kinetics of DPP-4 inhibition by gemigliptin was characterized by a fast association and a slow dissociation rate compared to sitagliptin (fast on and fast off rate) or vildagliptin (slow on and slow off rate). In addition, gemigliptin showed at least >23,000-fold selectivity for DPP-4 over various proteases and peptidases, including DPP-8, DPP-9, and fibroblast activation protein (FAP)-α. In the rat, dog, and monkey, gemigliptin showed more potent DPP-4 inhibitory activity in vivo compared with sitagliptin. In mice and dogs, gemigliptin prevented the degradation of active glucagon-like peptide-1 by DPP-4 inhibition, which improved glucose tolerance by increasing insulin secretion and reducing glucagon secretion during an oral glucose tolerance test. The long-term anti-hyperglycemic effect of gemigliptin was evaluated in diet-induced obese mice and high-fat diet/streptozotocin-induced diabetic mice. Gemigliptin dose-dependently decreased hemoglobin A1c (HbA1c) levels and ameliorated ß-cell damage. In conclusion, gemigliptin is a potent, long-acting, and highly selective DPP-4 inhibitor and can be a safe and effective drug for the long-term treatment of type 2 diabetes.

Computer-aided identification of new histone deacetylase 6 selective inhibitor with anti-sepsis activity.

Histone deacetylase (HDAC) inhibitors have been recognized as promising approaches to the treatment of various human diseases including cancer, inflammation, neurodegenerative diseases, and metabolic disorders. Several pan-HDAC inhibitors are currently approved only as anticancer drugs. Interestingly, SAHA (vorinostat), one of clinically available pan-HDAC inhibitors, shows an anti-inflammatory effect at concentrations lower than those required for inhibition of tumor cell growth. It was also reported that HDAC6 selective inhibitor tubastatin A has anti-inflammatory and anti-rheumatic effect. In our efforts to develop novel HDAC inhibitors, we rationally designed various HDAC inhibitors based on the structures of two hit compounds identified by virtual screening of chemical database. Among them, 9a ((E)-N-hydroxy-4-(2-styrylthiazol-4-yl)butanamide) was identified as a HDAC6 selective inhibitor (IC50 values of 0.199 µM for HDAC6 versus 13.8 µM for HDAC1), and it did not show significant cytotoxicity against HeLa cells. In vivo biological evaluation of 9a was conducted on a lipopolysaccharide (LPS)-induced mouse model of sepsis. The compound 9a significantly improved 40% survival rate (P = 0.0483), and suppressed the LPS-induced increase of TNF-α and IL-6 mRNA expression in the liver of mice. Our study identified novel HDAC6 selective inhibitor 9a, which may serve as a potential lead for the development of anti-inflammatory or anti-sepsis agents.

Trichostatin A Protects Liver against Septic Injury through Inhibiting Toll-Like Receptor Signaling.

Sepsis, a serious clinical problem, is characterized by a systemic inflammatory response to infection and leads to organ failure. Toll-like receptor (TLR) signaling is intimately implicated in hyper-inflammatory responses and tissue injury during sepsis. Histone deacetylase (HDAC) inhibitors have been reported to exhibit anti-inflammatory properties. The aim of this study was to investigate the hepatoprotective mechanisms of trichostatin A (TSA), a HDAC inhibitor, associated with TLR signaling pathway during sepsis. The anti-inflammatory properties of TSA were assayed in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Polymicrobial sepsis was induced in mice by cecal ligation and puncture (CLP), a clinically relevant model of sepsis. The mice were intraperitoneally received TSA (1, 2 or 5 mg/kg) 30 min before CLP. The serum and liver samples were collected 6 and 24-h after CLP. TSA inhibited the increased production of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in LPS-stimulated RAW264.7 cells. TSA improved sepsis-induced mortality, attenuated liver injury and decreased serum TNF-α and IL-6 levels. CLP increased the levels of TLR4, TLR2 and myeloid differentiation primary response protein 88 (MyD88) protein expression and association of MyD88 with TLR4 and TLR2, which were attenuated by TSA. CLP increased nuclear translocation of nuclear factor kappa B and decreased cytosolic inhibitor of kappa B (IκB) protein expression, which were attenuated by TSA. Moreover, CLP decreased acetylation of IκB kinase (IKK) and increased association of IKK with IκB and TSA attenuated these alterations. Our findings suggest that TSA attenuates liver injury by inhibiting TLR-mediated inflammatory response during sepsis.