Search

Ischemia and reperfusion-elicited tissue injury contributes to morbidity and mortality of hepatic surgery and during liver transplantation. Previous studies implicated extracellular adenosine signaling in liver protection. Based on the notion that extracellular adenosine signaling is terminated by uptake from the extracellular towards the intracellular compartment by way of equilibrative nucleoside transporters (ENTs), we hypothesized a functional role of ENTs in liver protection from ischemia. During orthotopic liver transplantation in humans, we observed higher expressional levels of ENT1 than ENT2, in conjunction with repression of ENT1 and ENT2 transcript and protein levels following warm ischemia and reperfusion. Treatment with the pharmacologic ENT inhibitor dipyridamole revealed elevations of hepatic adenosine levels and robust liver protection in a murine model of liver ischemia and reperfusion. Studies in gene-targeted mice for Ent1 or Ent2 demonstrated selective protection from liver injury in Ent1−/− mice. Treatment with selective adenosine receptor antagonists indicated a contribution of Adora2b receptor signaling in ENT-dependent liver protection. Conclusion: These findings implicate ENT1 in liver protection from ischemia and reperfusion injury and suggest ENT inhibitors may be of benefit in the prevention or treatment of ischemic liver injury. (Hepatology 2013;58:1766–1778)

Ischemia and reperfusion significantly contributes to the morbidity and mortality of liver surgery and transplantation. Based on studies showing a critical role for adenosine signaling in mediating tissue adaptation during hypoxia, we hypothesized that signaling events through adenosine receptors (ADORA1, ADORA2A, ADORA2B, or ADORA3) attenuates hepatic ischemia and reperfusion injury. Initial screening studies of human liver biopsies obtained during hepatic transplantation demonstrated a selective and robust induction of ADORA2B transcript and protein following ischemia and reperfusion. Subsequent exposure of gene-targeted mice for each individual adenosine receptor to liver ischemia and reperfusion revealed a selective role for the Adora2b in liver protection. Moreover, treatment of wild-type mice with an Adora2b-selective antagonist resulted in enhanced liver injury, whereas Adora2b-agonist treatment was associated with attenuated hepatic injury in wild-type, but not in Adora2b −/− mice. Subsequent studies in mice with Adora2b deletion in different tissues—including vascular endothelia, myeloid cells, and hepatocytes—revealed a surprising role for hepatocellular-specific Adora2b signaling in attenuating nuclear factor NF-κB activation and thereby mediating liver protection from ischemia and reperfusion injury. These studies provide a unique role for hepatocellular-specific Adora2b signaling in liver protection during ischemia and reperfusion injury.

Acute liver failure (ALF) is a severe life-threatening disease which usually arises in patients with-irreversible liver illnesses. Although human ectonucleotide triphosphate diphosphohydrolase-1, E-NTPDase1 (CD39) and ecto-5'-nucleotidase, Ecto5'NTase (CD73) are known to protect tissues from ALF, the expression and function of CD39 and CD73 during ALF are currently not fully investigated. We tested whether CD39 and CD73 are upregulated by hypoxia inducible factor (HIF)-1α, and improve ischemic tolerance to ALF. To test our hypothesis, liver biopsies were obtained and we found that CD39 and CD73 mRNA and proteins from human specimens were dramatically elevated in ALF. We investigated that induction of CD39 and CD73 in ALF-related with wild type mice. In contrast, deletion of cd39 and cd73 mice has severe ALF. In this study, we concluded that CD39 and CD73 are molecular targets for the development of drugs for ALF patients care.

Backgrounds/Aims Nucleos(t)ide analogues (NUCs) effectively suppress hepatitis B virus (HBV) replication, but hepatocellular carcinoma (HCC) recurrence often leads to HBV replication despite NUC therapy. The aim of this study was to determine whether high-dose tenofovir (TNF) therapy can suppresses HCC recurrence-associated HBV replication. Methods We performed a single-arm prospective study to assess the clinical feasibility of high-dose TNF (hdTNF). We recruited 10 patients during September 2015 and followed up for 3 months or early drop-out. Results All 10 patients had HCC of advanced stages due to HCC recurrence and gradual progression. The average age of patients was 51.2±4.7 years and 9 were male. Three patients did not tolerate the increased TNF dosage and were dropped out early. The other 7 patients were relatively tolerable to the increased dosage of TNF 5 tablets per day. One patient had mild gastrointestinal symptoms and another patient complained of insomnia. Increased HBV replication and HCC progression was observed despite hdTNF for 4-8 weeks. All 7 patients showed tumor progression during the 3 month follow-up. In these patients, blood HBV DNA before hdTNF was 50-200 copies/ml; and 4-8 weeks after hdTNF, the HBV replication status was not improved with blood HBV DNA of 50-300 copies/ml. This clinical study was terminated early after these negative results were confirmed. Conclusions The results of this study indicated that high dose of TNF up to 5-fold the recommended dosage is not tolerated by a considerable proportion of patients and also ineffective in suppressing HCC progression-associated HBV replication.

Renal ischemia is among the leading causes of acute kidney injury (AKI). Previous studies have shown that extracellular adenosine is a prominent tissue-protective cue elicited during ischemia, including signaling events through the adenosine receptor 2b (Adora2b). To investigate the functional role of Adora2b signaling in cytokine-mediated inflammatory pathways, we screened wild-type and Adora2b-deficient mice undergoing renal ischemia for expression of a range of inflammatory cytokines. These studies demonstrated a selective and robust increase of TNF-α levels in Adora2b-deficient mice following renal ischemia and reperfusion. Based on these findings, we next sought to understand the contribution of TNF-α on ischemic AKI through a combination of loss- and gain-of-function studies. Loss of TNF-α, through either Ab blockade or study of Tnf-α–deficient animals, resulted in significantly attenuated tissue injury and improved kidney function following renal ischemia. Conversely, transgenic mice with overexpression of TNF-α had significantly pronounced susceptibility to AKI. Furthermore, neutrophil depletion or reconstitution of Adora2b−/− mice with Tnf-α–deficient neutrophils rescued their phenotype. In total, these data demonstrate a critical role of adenosine signaling in constraining neutrophil-dependent production of TNF-α and implicate therapies targeting TNF-α in the treatment of ischemic AKI.

Background & Aims Human carbonyl reductase1 (CBR1) has been reported to protect cells against lipid peroxidation. Since human hepatocellular carcinoma (HCC) cells are under oxidative stress in hypoxic conditions, we tested if CBR1 is upregulated by hypoxia inducible factor (HIF)-1α, helps tumor growth under hypoxia, and renders chemoresistance to cisplatin and doxorubicin in HCC. Methods Luciferase, EMSA, and chromatin immunoprecipitation (ChIP) assays were performed to analyze whether HIF-1α transactivates CBR1 promoter. CBR1 overexpression, siRNA, and inhibitors were used to study the role of CBR1 in tumor survival under hypoxia and chemoresistance to cisplatin and doxorubicin in HCC. FACS and Western blot analysis for oxidative stress markers were performed to measure ROS. Immunohistochemistry (IHC) was performed to analyze CBR1 expression in 78 cases of HCC and 123 cases of colon cancer tissues. Results The CBR1 promoter was activated by HIF-1α. CBR1 overexpression enhanced cell survival by decreasing oxidative stress under hypoxia, cisplatin, and doxorubicin treatment. CBR1 -siRNA increased apoptosis via increasing oxidative stress. Combinational therapy of CBR1 inhibitors with cisplatin or doxorubicin enhanced cell death in HCC cells. IHC showed CBR1 overexpression in 56 (72%) out of 78 HCC and 88 (72%) out of 123 colon cancer cases. Conclusions Overexpressed CBR1 by HIF-1α plays important roles in tumor growth under hypoxia and chemoresistance to anticancer drugs. The inhibition of CBR1 by specific inhibitors enhances anticancer drug efficacy in HCC. Therefore, we concluded that CBR1 is a good molecular target for the development of anticancer drugs for HCC patients.

Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras (c-Ras) in muscle differentiation remains unclear. The active GTP-bound form of Ras has been known to associate with diverse effectors including Raf, phosphatidylinositol 3-kinase (PI3K), Ral-GDS, and other molecules to transmit downstream signals. We hypothesize that c-Ras may stimulate muscle differentiation by selectively activating PI3K, an important mediator for muscle differentiation. In our experiments, inhibition of c-Ras by farnesyltransferase inhibitors and a dominant negative form of H-Ras (Ras S17N) suppressed muscle differentiation. Consistently, individual knockdown of H-Ras, K-Ras, and N-Ras by siRNAs all blocked muscle differentiation. Interestingly, we found that c-Ras preferentially interacts with PI3K rather than its major binding partner c-Raf, during myogenic differentiation, with total c-Ras activity remaining unchanged. PI3K and its downstream myogenic pathway, the Nox2/NF-kappaB/inducible nitric oxide synthase (iNOS) pathway, were found to be suppressed by inhibition of c-Ras activity during differentiation. Furthermore, expression of a constitutively active form of PI3K completely rescued the differentiation block and reactivated the Nox2/NF-kappaB/iNOS pathway in c-Ras-inhibited cells. On the basis of our results, we conclude that contrary to oncogenic Ras, proto-oncogenic H-Ras, K-Ras, and N-Ras are directly involved in the promotion of muscle differentiation via PI3K and its downstream signaling pathways. In addition, PI3K pathway activation is associated with a concurrent suppression of the otherwise predominantly activated Raf/Mek/Erk pathway.

Vitamin K plays a role in controlling cell growth. Anti-angiogenic effects of sorafenib lead to impairment of vitamin K uptake and induction of des-γ-carboxyprothrombin release by hepatocellular carcinoma (HCC) cells. We examined sorafenib and vitamin K individually and in combination regarding their ability to suppress migration and metastatic potential of HCC cells. HepG2 cells (HCC cell line) were treated with hepatocyte growth factor (HGF). E-Cadherin expression, phospho-MET (p-MET), and phospho-extracellular signal-regulated kinase (p-ERK) levels and cell migration were evaluated. HGF-stimulated HepG2 cells, which were treated with a combination of sorafenib and vitamin K, showed significantly increased expression of E-cadherin and impairment of migration ability compared to when treated with either agent alone. This combination therapy also induced marked inhibition of epithelial-mesenchymal transition phenotype; inhibition of HGF-stimulated cell proliferation, invasion and migration; and inhibition of HGF/c-MET signaling pathway. Levels of p-MET and p-ERK were also significantly reduced by this combination. Our experimental study demonstrated that sorafenib and vitamin K can function synergistically to inhibit the migration and proliferation of HCC cells. Combination therapy with sorafenib and vitamin K appears to be worthy of clinical trial with expectation of synergistic therapeutic effects.

Sorafenib increases survival of patients with advanced hepatocellular carcinoma (HCC) by inhibiting RAF kinase and receptor tyrosine kinase activity, but involvement of sorafenib in fibrosis and epithelial-mesenchymal transition (EMT) remains unclear. To elucidate effects of sorafenib on EMT progression and matrix metalloproteinase (MMP) activity, levels of E-cadherin, N-cadherin, and MMPs were evaluated in HepG2 human HCC cells induced by hepatocyte growth factor (HGF). Scratching cell migration assay, matrigel cell invasion assay, and immuno histochemistry were performed to examine effects of sorafenib on tumor metastasis and MMP expression. Sorafenib inhibited HGF-induced EMT and suppressed cell migration and invasion. Treatment with sorafenib significantly reduced HGF-enhanced expression of MMPs, suggesting that inhibition of MMP activity contributes to suppression of cellular motility and invasiveness of HepG2 cells. Neutralization of MMP activity by antibodies to MMP2/9, broad-spectrum MMP inhibitor or selective gelatinase inhibitor resulted in significant suppression of HGF-induced EMT and cell migration/invasion. Sorafenib treatment and MMP inactivation inhibited HGF-induced c-MET and MEK/ERK pathways. Sorafenib reduced MMP activity in this HGF-induced tumorigenic model of HCC. These findings provide in vitro evidence that sorafenib suppresses HGF-induced EMT and cell migration/invasion, as well as HGF-induced c-MET and MEK/ERK pathways.

ABO incompatibility is no longer considered a contraindication for adult living donor liver transplantation (ALDLT) due to various strategies to overcome the ABO blood group barrier. We report the largest single-center experience of ABO-incompatible (ABOi) ALDLT in 235 adult patients. The desensitization protocol included a single dose of rituximab and total plasma exchange. In addition, local graft infusion therapy, cyclophosphamide, or splenectomy was used for a certain time period, but these treatments were eventually discontinued due to adverse events. There were three cases (1.3%) of in-hospital mortality. The cumulative 3-year graft and patient survival rates were 89.2% and 92.3%, respectively, and were comparable to those of the ABO-compatible group (n = 1301). Despite promising survival outcomes, 17 patients (7.2%) experienced antibody-mediated rejection that manifested as diffuse intrahepatic biliary stricture; six cases required retransplantation, and three patients died. ABOi ALDLT is a feasible method for expanding a living liver donor pool, but the efficacy of the desensitization protocol in targeting B cell immunity should be optimized.

A complex biologic network regulates kidney perfusion under physiologic conditions. This system is profoundly perturbed following renal ischemia, a leading cause of acute kidney injury (AKI) - a life-threatening condition that frequently complicates the care of hospitalized patients. Therapeutic approaches to prevent and treat AKI are extremely limited. Better understanding of the molecular pathways promoting postischemic reflow could provide new candidate targets for AKI therapeutics. Due to its role in adapting tissues to hypoxia, we hypothesized that extracellular adenosine has a regulatory function in the postischemic control of renal perfusion. Consistent with the notion that equilibrative nucleoside transporters (ENTs) terminate adenosine signaling, we observed that pharmacologic ENT inhibition in mice elevated renal adenosine levels and dampened AKI. Deletion of the ENTs resulted in selective protection in Ent1-/- mice. Comprehensive examination of adenosine receptor-knockout mice exposed to AKI demonstrated that renal protection by ENT inhibitors involves the A2B adenosine receptor. Indeed, crosstalk between renal Ent1 and Adora2b expressed on vascular endothelia effectively prevented a postischemic no-reflow phenomenon. These studies identify ENT1 and adenosine receptors as key to the process of reestablishing renal perfusion following ischemic AKI. If translatable from mice to humans, these data have important therapeutic implications.

Although acute lung injury (ALI) contributes significantly to critical illness, resolution often occurs spontaneously through endogenous pathways. We recently found that mechanical ventilation increases levels of pulmonary adenosine, a signaling molecule known to attenuate lung inflammation. In this study, we hypothesized a contribution of transcriptionally controlled pathways to pulmonary adenosine receptor (ADOR) signaling during ALI. We gained initial insight from microarray analysis of pulmonary epithelia exposed to conditions of cyclic mechanical stretch, a mimic for ventilation-induced lung disease. Surprisingly, these studies revealed a selective induction of the ADORA2B. Using real-time RT-PCR and Western blotting, we confirmed an up to 9-fold induction of the ADORA2B following cyclic mechanical stretch (A549, Calu-3, or human primary alveolar epithelial cells). Studies using ADORA2B promoter constructs identified a prominent region within the ADORA2B promoter conveying stretch responsiveness. This region of the promoter contained a binding site for the transcription factor hypoxia-inducible factor (HIF)-1. Additional studies using site-directed mutagenesis or transcription factor binding assays demonstrated a functional role for HIF-1 in stretch-induced increases of ADORA2B expression. Moreover, studies of ventilator-induced lung injury revealed induction of the ADORA2B during ALI in vivo that was abolished following HIF inhibition or genetic deletion of Hif1a. Together, these studies implicate HIF in the transcriptional control of pulmonary adenosine signaling during ALI.

Nucleotide phosphohydrolysis by the ecto-5'-nucleotidase (CD73) is the main source for extracellular generation of adenosine. Extracellular adenosine subsequently signals through four distinct adenosine A receptors (Adora1, Adora2a, Adora2b, or Adora3). Here, we hypothesized a functional role for CD73-dependent generation and concomitant signaling of extracellular adenosine during diabetic nephropathy. CD73 transcript and protein levels were elevated in the kidneys of diabetic mice. Genetic deletion of CD73 was associated with more severe diabetic nephropathy, whereas treatment with soluble nucleotidase was therapeutic. Transcript levels of renal adenosine receptors showed a selective induction of Adora2b during diabetic nephropathy. In a transgenic reporter mouse, Adora2b expression localized to the vasculature and increased after treatment with streptozotocin. Adora2b(-/-) mice experienced more severe diabetic nephropathy, and studies in mice with tissue-specific deletion of Adora2b in tubular epithelia or vascular endothelia implicated endothelial Adora2b signaling in protection from diabetic nephropathy. Finally, treatment with a selective Adora2b agonist (BAY 60-6583) conveyed potent protection from diabetes-associated kidney disease. Taken together, these findings implicate CD73-dependent production of extracellular adenosine and endothelial Adora2b signaling in kidney protection during diabetic nephropathy.

Recent studies implicate neuronal guidance molecules in the orchestration of inflammatory events. For example, previous studies demonstrate a functional role for netrin-1 in attenuating acute kidney injury. Here, we hypothesized a kidney-protective role for netrin-1 during chronic kidney disease, such as occurs during diabetic nephropathy. To study the role of netrin-1 during diabetic nephropathy, we induced diabetes in mice at the age of 8 weeks by streptocotozin (STZ) treatment. Sixteen weeks after STZ treatment, we examined the kidneys. Initial studies in wild-type mice demonstrated robust induction of renal, urinary, and plasma netrin-1 protein levels during diabetic nephropathy. Subsequent genetic studies in mice with partial netrin-1 deficiency (Ntrn1 +/− mice) revealed a more severe degree of diabetic nephropathy, including more severe loss of kidney function (albuminuria, glomerular filtration rate, histology). We subsequently performed pharmacologic studies with recombinant netrin-1 treatment given continuously via osmotic pump. Indeed, netrin-1 treatment was associated with attenuated albuminuria and improved histologic scores for diabetic nephropathy compared to controls. Consistent with previous studies implicating purinergic signaling in netrin-1-elicited tissue protection, mice deficient in the Adora2b adenosine receptor were not protected. Taken together, these studies demonstrate a functional role for endogenous netrin-1 in attenuating diabetic kidney disease.

Mitochondrial reactive oxygen species (mROS) have been considered detrimental to cells. However, their physiological roles as signaling mediators have not been thoroughly explored. Here, we investigated whether mROS generated from mitochondrial electron transport chain (mETC) complex I stimulated muscle differentiation. Our results showed that the quantity of mROS was increased and that manganese superoxide dismutase (MnSOD) was induced via NF-κB activation during muscle differentiation. Mitochondria-targeted antioxidants (MitoQ and MitoTEMPOL) and mitochondria-targeted catalase decreased mROS quantity and suppressed muscle differentiation without affecting the amount of ATP. Mitochondrial alterations, including the induction of mitochondrial transcription factor A and an increase in the number and size of mitochondria, and functional activations were observed during muscle differentiation. In particular, increased expression levels of mETC complex I subunits and a higher activity of complex I than other complexes were observed. Rotenone, an inhibitor of mETC complex I, decreased the mitochondrial NADH/NAD(+) ratio and mROS levels during muscle differentiation. The inhibition of complex I using small interfering RNAs and rotenone reduced mROS levels, suppressed muscle differentiation, and depleted ATP levels with a concomitant increase in glycolysis. From these results, we conclude that complex I-derived O(2)·(-), produced through reverse electron transport due to enhanced metabolism and a high activity of complex I, was dismutated into H(2)O(2) by MnSOD induced via NF-κB activation and that the dismutated mH(2)O(2) stimulated muscle differentiation as a signaling messenger.

The expression of glutathione-S-transferase (GST) fusion protein is extensively utilized in the study of protein-protein interactions. In the commonly used purification method, the overexpressed GST fusion protein is bound to the glutathione (GSH)-coupled resins via affinity chromatography, and then eluted by an excessive quantity of reduced GSH. However, this technique has certain limitations, such as low product purity, retention of GSH in the sample, as well as relatively high cost. To overcome these limitations, in this study, elution buffer containing 2% formic acid was utilized rather than GSH to elute the GST-fusion protein, and thereafter the acidic samples were neutralized using collecting buffer. By using this method, highly purified GST-cyclophilin A (CypA) fusion protein was obtained, without affecting the structural and functional characteristics such as PPIase and chaperone activities. Moreover, the procedure is also cost-effective, due to the low cost of formic acid as compared with GSH.

Backgrounds/Aims: We evaluated the clinical usability of immune cell monitoring in adult liver transplantation (LT) recipients. Methods: This study was composed of two parts as using calcineurin phosphatase (CNP) activity assay and ImmuKnow assay independently as in vitro monitoring tools of immune cell function in adult LT recipients. Results: There was a rough correlation between CNP activity and tacrolimus concentration in 33 patients. This association was evident in patients who were only administered tacrolimus, but disappeared after the co-administration of mycophenolate. In 118 healthy individuals, the mean proportion of helper T-cells was 37.4±8.1%. According to ImmuKnow assay, their immune responses were strong in 12 patients (10.2%), moderate in 92 patients (78.0%), and low in 14 patients (11.9%). In 85 patients waiting for LT, there was a rough correlation between the ImmuKnow ATP level and age. Their immune responses were strong in 0 patients (0%), moderate in 8 patients (9.4%), and low in 77 patients (90.6%). There was a difference in the ImmuKnow ATP levels between healthy individuals and patients with liver disease. In 137 LT recipients, there was no correlation between the ImmuKnow ATP levels and tacrolimus concentration. This trend did not change after grouping the patients according to co-administration with mycophenolate. Eight recipients experienced acute rejection, but none showed strong immune response. Conclusions: We think that both CNP activity assay and ImmuKnow assay are too limited to objectively determine the level of immunosuppression. Further studies should be performed to identify other methods for immune function monitoring.