Analysis of In Vivo Nuclear Factor-κB Activation during Liver Inflammation in Mice: Prevention by Catalase Delivery

Knockdown of TRAF6 inhibits chondrocytes apoptosis and inflammation by suppressing the NF-κB pathway in lumbar facet joint osteoarthritis

Tumor necrosis factor receptor-associated factor 6 (TRAF6), a regulator of NF-κB signaling, has been discovered recently to be probably related to osteoarthritis, while the function of TRAF6 in lumbar facet joint osteoarthritis(FJOA)still remains unknown. The aim of this study was to probe the specific function of TRAF6 in chondrocytes and its connection with the pathophysiology of FJOA. We found upregulation of TRAF6 in FJOA cartilage by western blot analysis. In vitro, we stimulated immortalized human chondrocytes by LPS to establish the cells apoptosis model. Western blot analysis demonstrated that levels of TRAF6 and cleaved caspase-3/8 in the chondrocyte injury model increased significantly. Knockdown of TRAF6 suppressed the expression of matrix metallopeptidase-13 (MMP-13) and interleukin-6 (IL-6) induced by LPS, and alleviated cell apoptosis. Meanwhile, western blot and immunofluorescent staining demonstrated that IκBα degradation and p65 nuclear transportation were also inhibited, revealing that knockdown of TRAF6 suppressed activation of the NF-κB pathway in LPS-induced chondrocytes apoptosis model. Collectively, our findings suggest that TRAF6 plays a crucial role in FJOA development by regulating NF-κB signaling pathway. Knockdown of TRAF6 may supply a potential therapeutic strategy for FJOA.

The effect of immobilized antioxidant enzymes on the oxidative stress in UV-irradiated rat skin

Aim: Superoxide dismutase (SOD) and catalase (CAT) immobilized on gold nanoparticles (AuNP) and silver nanoparticles (AgNP) nanoparticles were used to reduce UV radiation-induced oxidative stress in rat skin. Materials & methods: The antioxidant influence of the enzymes was investigated on level of malondialdehyde, 8-hydroksy-2'deoksyguanozine, myeloperoxidase, total antioxidant capacity, SOD2 and CAT activity and expression, and glutathione and glutathione peroxidase activity. Results: The application of immobilized SOD and CAT on UV-irradiated skin reduced malondialdehyde and 8-hydroksy-2'deoksyguanozine levels also SOD and CAT activity and expression increased. The tested enzymes influence glutathione peroxidase activity and level of total antioxidant capacity and glutathione. Conclusion: Immobilized enzymes increased the antioxidative potential of skin following UV irradiation.

HIF-mediated increased ROS from reduced mitophagy and decreased catalase causes neocytolysis

During prolonged hypoxia, hypoxia-inducible factors (HIFs) mediate an increase in erythropoiesis, leading to an increased red blood cell (RBC) mass and polycythemia. Upon return to normoxia, the increased RBC mass is abruptly overcorrected by the preferential destruction of hypoxia-formed young RBCs, a phenomenon termed neocytolysis. The molecular and biochemical mechanisms involved in neocytolysis are unknown. We developed a murine model of neocytolysis by exposing mice to 12 % oxygen for 10 days followed by return to normoxia. Upon return to normoxia, there was excessive accumulation of reactive oxygen species (ROS) in RBCs from an increased reticulocyte mitochondrial mass correlating with decreased Bnip3L transcripts (Bnip3L mediates reticulocyte mitophagy) and reduced catalase activity. During hypoxia, upregulated miR-21 resulted in low catalase activity in young RBCs. Furthermore, neocytolysis was attenuated by antioxidants and plasma catalase and blunted in mice that had constitutively high expression of HIFs. Among human neonates studied, we report data supporting the existence of neocytolysis during the first week of life. Together, these experiments indicate that the major mechanisms causing neocytolysis involve (1) production of young RBCs with low catalase during hypoxia and (2) lysis of the young RBCs after return to normoxia, mediated by ROS from an increased mitochondrial mass.

KEY MESSAGES

We report a mouse model of neocytolysis. Neocytolysis is caused by excessive ROS formation mediated by HIF. ROS is generated from increased mitochondria in reticulocytes. Hypoxia-generated RBCs have low catalase and are preferentially destroyed. Reduced catalase is regulated by increased microRNA-21.

Dynamic imaging of pancreatic nuclear factor κB (NF-κB) activation in live mice using adeno-associated virus (AAV) infusion and bioluminescence

Nuclear factor κB (NF-κB) is an important signaling molecule that plays a critical role in the development of acute pancreatitis. Current methods for examining NF-κB activation involve infection of an adenoviral NF-κB-luciferase reporter into cell lines or electrophoretic mobility shift assay of lysate. The use of adeno-associated viruses (AAVs) has proven to be an effective method of transfecting whole organs in live animals. We examined whether intrapancreatic duct infusion of AAV containing an NF-κB-luciferase reporter (AAV-NF-κB-luciferase) can reliably measure pancreatic NF-κB activation. We confirmed the infectivity of the AAV-NF-κB-luciferase reporter in HEK293 cells using a traditional luciferase readout. Mice were infused with AAV-NF-κB-luciferase 5 weeks before induction of pancreatitis (caerulein, 50 μg/kg). Unlike transgenic mice that globally express NF-κB-luciferase, AAV-infused mice showed a 15-fold increase in pancreas-specific NF-κB bioluminescence following 12 h of caerulein compared with baseline luminescence (p < 0.05). The specificity of the NF-κB-luciferase signal to the pancreas was confirmed by isolating the pancreas and adjacent organs and observing a predominant bioluminescent signal in the pancreas compared with liver, spleen, and stomach. A complementary mouse model of post-ERCP-pancreatitis also induced pancreatic NF-κB signals. Taken together these data provide the first demonstration that NF-κB activation can be examined in a live, dynamic fashion during pancreatic inflammation. We believe this technique offers a valuable tool to study real-time activation of NF-κB in vivo.

Development of PEGylated serum albumin with multiple reduced thiols as a long-circulating scavenger of reactive oxygen species for the treatment of fulminant hepatic failure in mice

Reactive oxygen species (ROS) are involved in the pathophysiology of fulminant hepatic failure. Therefore, we developed polyethylene glycol-conjugated bovine serum albumin with multiple reduced thiols (PEG-BSA-SH) for the treatment of fulminant hepatic failure. As a long-circulating ROS scavenger, PEG-BSA-SH effectively scavenged highly reactive oxygen species and hydrogen peroxide in buffer solution. PEG-BSA-SH showed a long circulation time in the plasma after intravenous injection into mice. Fulminant hepatic failure was induced by intraperitoneal injection of lipopolysaccharide and D-galactosamine (LPS/D-GalN) into mice. The LPS/D-GalN-induced elevation of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels was significantly inhibited by a bolus intravenous injection of PEG-BSA-SH. Furthermore, the changes in hepatic lipid peroxide and hepatic blood flow were effectively suppressed by PEG-BSA-SH. In contrast, L-cysteine, glutathione, and dithiothreitol, three traditional reduced thiols, had no statistically significant effects on the serum levels of ALT or AST. These findings indicate that PEG-BSA-SH is a promising ROS scavenger and useful in the treatment of fulminant hepatic failure.

Establishment of stable reporter expression for in vivo imaging of nuclear factor-κB activation in mouse liver

The nuclear factor-κB (NF-κB) signaling pathway plays a critical role in a multitude of cellular processes. Activation of the NF-κB transcription factor family is essential for the initiation of inflammation, immunity, cell proliferation and apoptosis through a list of responsive genes. In hepatic tissue, activation of the NF-κB pathway has been implicated in a number of pathological conditions. Here we described a mouse model for noninvasive quantification of NF-κB activation in the hepatic tissues. Mice were subjected to hydrodynamic delivery with a mixture of pattB-NF-κB-Fluc reporter and φC31o integrase vector. Hepatic expression of φC31o integrase mediated chromosomal integration of the pattB-NF-κB-Fluc reporter, resulting in stable luciferase expression at 300 days post transfection. We applied noninvasive imaging and were able to detect NF-κB activation under acute liver injury and hepatitis conditions. During hepatectomy-induced liver regeneration, NF-κB activation was detected locally in the tissues at the surgery site. Treatment with Sorafenib suppressed NF-κB activation, accompanied with perturbation of liver regeneration. In conclusion, we established a method for stable transfection of the hepatic tissues and applied the transfected mice to longitudinal monitoring of NF-κB activity under pathological conditions. Further exploration of this methodology for establishment of other disease models and for evaluation of novel pharmaceuticals is likely to be fruitful.

Luminescence-based in vivo monitoring of NF-κB activity through a gene delivery approach

Background

Monitoring activity of specific signaling pathways in vivo is challenging and requires highly sensitive methods to detect dynamic perturbations in whole organisms.

Results

In vivo gene delivery of a luciferase reporter followed by bioluminiscence imaging allows measuring NF-κB activity in mice liver and lungs.

Conclusions

This protocol allows a direct measure of NF-κB activity through quantification of bioluminescence signal, demonstrating its accuracy and sensitivity in different animal models and experimental conditions. Variants could be also applied for the analysis of NF-κB activity in different tissues or for studying other signaling pathways in vivo.

Anti-carcinogenic action of curcumin by activation of antioxidant defence system and inhibition of NF-κB signalling in lymphoma-bearing mice

NF-κB (nuclear factor κB) plays a significant role in inflammation, immunity, cell proliferation, apoptosis and malignancy. ROS (reactive oxygen species) are among the most important regulating factors of NF-κB. Intracellular ROS are mainly regulated by an endogenous antioxidant defence system. Any disruption of redox balance leads to oxidative stress, which causes a number of pathological conditions including inflammation and malignancy. Increased metabolic activity in cancerous cells leads to oxidative stress, which is further enhanced due to depletion of the endogenous antioxidant defence system. However, the activation and signalling of NF-κB are reported to be inhibited by overexpression and induced activity of antioxidant enzymes. Therefore the present study focuses on the correlation between the endogenous antioxidant defence system, ROS and NF-κB activation during lymphoma growth in mice. The study highlights the anti-carcinogenic role of curcumin by modulation of NF-κB activation and oxidative stress via the endogenous antioxidant defence system. Oxidative stress was monitored by lipid peroxidation, protein carbonylation and antioxidant enzyme activity. NF-κB-mediated signalling was tested by DNA-binding activity. The results reflect that intracellular production of H2O2 in oxidative tumour micro-environment regulates NF-κB activation. Curcumin inhibits oxidative state in the liver of lymphoma-bearing mice by enhancing the transcription and activities of antioxidant enzymes, which in turn modulate activation of NF-κB, leading to a decrease in lymphoma growth. Morphological changes as well as cell proliferation and cell survival assays confirmed reduced lymphoma growth. Thus curcumin contributes to cancer prevention by disrupting the vicious cycle of constant ROS production, responsible for a high oxidative micro-environment for tumour growth.

Thioacetamide intoxication triggers transcriptional up-regulation but enzyme inactivation of UDP-glucuronosyltransferases

Thioacetamide (TAA) is a potent hepatotoxicant and has been widely used to develop experimental liver fibrosis/cirrhosis models. Although the liver toxicity of TAA has been extensively studied, little is known about its potential influence on UDP-glucuronosyltransferases (UGTs) associated with the development of liver fibrosis. The study presented here aimed to uncover the regulation patterns of UGTs in TAA-induced liver fibrosis of rats. Potential counteracting effects of hepatoprotective agents were also determined. TAA treatment for 8 weeks induced a significant transcriptional up-regulation of the major UGT isoforms, including UGT1A1, UGT1A6, and UGT2B1, accompanied with the dramatic elevations of most typical serum biomarkers of liver function and fibrosis scores. Upon TAA intoxication, the mRNA and protein levels of the major UGT isoforms were increased to 1.5- to 2.5-fold and 2.5- to 3.3-fold of that of the normal control, respectively. The hepatoprotective agents Schisandra spp. lignans extract and dimethyl diphenyl bicarboxylate could largely abolish TAA-induced up-regulation of all three UGT isoforms. However, enzyme activities of UGTs remained unchanged after TAA treatment. The dissociation of protein expression and enzyme activity could possibly be attributed to the inactivating effects of TAA, upon a NADPH-dependent bioactivation, on UGTs. This study suggests that the transcriptional up-regulation of UGTs may be an alternative mechanism of their preserved activities in liver fibrosis/cirrhosis.

Comparison of the type of liposome involving cytokine production induced by non-CpG Lipoplex in macrophages

To improve the transfection efficiency of plasmid DNA (pDNA) into cells, various types of cationic liposome have been used to prepare pDNA/cationic liposome complexes (lipoplexes). It is well-known that lipoplexes induce a large amount of proinflammatory cytokines because unmethylated CpG dinucleotides (CpG motifs) abundantly present in pDNA are recognized by Toll-like receptor-9 (TLR9) expressed in immune cells such as macrophages and dendritic cells. This nonspecific cytokine production is problematic in nonviral gene therapy. Moreover, recent studies have demonstrated that lipoplexes induce not only proinflammatory cytokines but also another type of cytokine, type I interferons (IFNs), irrespective of the frequency of CpG motifs in DNA and the expression of TLR9. To gain more insight into the CpG motif- and TLR9-independent induction of type I IFNs and proinflammatory cytokines by lipoplex, macrophage activation was evaluated in vitro using various cationic liposomes complexed with pDNA containing no CpG motifs. The production of IFN-beta, TNF-alpha and IL-6 by lipoplex was confirmed to be induced independently of the interaction between CpG DNA and TLR9 in macrophages from TLR9-knockout mice. Then, the release of the cytokines, the mRNA expression of Z-DNA binding protein-1 (Zbp1), a cytosolic double-stranded DNA sensor, and the cellular uptake of pDNA were examined in a macrophage-like cell line, RAW264.7. The level of cytokine production and the increase in the Zbp1 mRNA varied depending on the type of cationic liposome used. A good correlation was observed between the cytokine level and the Zbp1 mRNA. A confocal microscopic study using fluorescently labeled pDNA complexes showed that the complexes that released a lot of cytokines showed an enhanced distribution of pDNA-derived fluorescence into the cytosol. These results suggest that different intracellular trafficking derived from the type of liposomes determines the recognition of pDNA by ZBP1 after uptake of lipoplexes by the macrophages, followed by the release of type I IFNs and inflammatory cytokines. The present study demonstrates that cationic liposomes should be selected based on these findings for optimization of DNA-based therapies using lipoplexes.

Molecular imaging of transcriptional regulation during inflammation

Molecular imaging enables non-invasive visualization of the dynamics of molecular processes within living organisms in vivo. Different imaging modalities as MRI, SPECT, PET and optic imaging are used together with molecular probes specific for the biological process of interest. Molecular imaging of transcription factor activity is done in animal models and mostly in transgenic reporter mice, where the transgene essentially consists of a promoter that regulates a reporter gene. During inflammation, the transcription factor NF-κB is widely involved in orchestration and regulation of the immune system and almost all imaging studies in this field has revolved around the role and regulation of NF-κB. We here present a brief introduction to experimental use and design of transgenic reporter mice and a more extensive review of the various studies where molecular imaging of transcriptional regulation has been applied during inflammation.

Establishment of a guinea pig model of latent tuberculosis with GFP-introduced Mycobacterium tuberculosis

There exists latent tuberculosis, in which small numbers of tubercle bacilli remain viable in the host without visible granulomatous lesions. As few data exist on the mechanisms of latent tuberculosis, it is important to examine latent tuberculosis in terms of pathogenesis and efficacy of chemotherapy. As a first step, we used green fluorescent protein (GFP)-introduced H37Rv Mycobacterium tuberculosis to establish latent tuberculosis in the guinea pig that provides one of the best animal models of tuberculosis. We inoculated the guinea pigs subcutaneously with 100 or 1,000 colony-forming unit (CFU) of tubercle bacilli. During the 300-day follow-up period after infection, there were no clinical signs of disease, suggesting a lack of visible granulomatous lesions. In fact, upon necropsy, no macroscopic tuberculous lesions were recognized, but histopathological examination of the lung, spleen and liver revealed microgranulomas consisting of epithelioid macrophages and lymphocytes without central necrosis. Importantly, photon imaging visualized granulomatous lesions corresponding to these histologically apparent microgranulomas. Tuberculin skin testing of infected guinea pigs showed strong positivity (> or = 10 mm induration) until the end of the experiments. Real-time PCR analysis showed a significant increase in the expression levels of interferon-gamma, tumor necrosis factor-alpha, interleukin-12, and inducible nitric oxide synthase mRNAs in infected lung tissues after 300 days (P < 0.01). As human samples are hardly available to study latent tuberculosis, our guinea pig model would be useful for examining the pathogenesis and molecular mechanisms of latent tuberculosis as well as for monitoring the results of chemotherapy with green fluorescence emission of tubercle bacilli.

Reactivation of silenced transgene expression in mouse liver by rapid, large-volume injection of isotonic solution

Rapid, large-volume injection, or so-called hydrodynamic injection, of naked plasmid DNA gives high transgene expression in mouse liver, and this method has been applied to liver-directed gene transfer in humans with slight modifications. To prove that injection-induced biological changes are involved in hydrodynamic injection-induced, high-level transgene expression in mouse liver, isotonic solutions were injected into mice that had received a hydrodynamic injection of plasmid DNA. Transgene expression in the liver was increased by such injections irrespective of the cDNA, promoter, and type of solution. This reactivation was repeatable and detectable even 3 months after gene transfer. Parameters required for reactivation were similar to those required for the hydrodynamic injection of plasmid DNA. Plasmid DNA-polyethyleneimine complex-based transgene expression in mouse liver was also reactivated by the same treatment. DNA microarray and quantitative RT-PCR analyses revealed that the expression of immediate-early response genes c-fos and c-jun was increased 70 and 100-fold, respectively. Activator protein (AP)-1- or nuclear factor (NF)-kappa B-dependent transgene expression was increased by an injection of isotonic solutions. These findings indicate for the first time that a rapid, large-volume injection of isotonic solution activates the transcription factors AP-1 and NF-kappa B in the liver, which in turn increases the transcription of genes delivered by hydrodynamic injection or other methods.

Catalase delivery for inhibiting ROS-mediated tissue injury and tumor metastasis

Reactive oxygen species (ROS) have been suggested to be involved in a variety of human diseases. Catalase, an enzyme degrading hydrogen peroxide, can be used as a therapeutic agent for such diseases, but its successful application will depend on the distribution of the enzyme to the sites where ROS are generated. Chemical modification techniques have been used to control the tissue distribution of catalase, and delivery to hepatocytes (galactosylation), liver nonparenchymal cells (mannosylation or succinylation), kidney (cationization) and the blood pool (PEGylation) has been achieved. The effectiveness of catalase delivery has been demonstrated in animal models for hepatic ischemia/reperfusion injury, chemical-induced tissue injuries and tumor metastasis to the liver, lung and peritoneal organs. Significant inhibition was observed in the ROS-mediated oxidative tissue damages and ROS-mediated upregulation of expression of genes responsible for recruitment of inflammatory cells and for metastatic growth of tumor cells. Because oxygen plays a fundamental key role in our life and oxidative stress is implicated in a wide variety of human diseases, catalase delivery could have wide application in the near future.

Hydrogen peroxide-mediated nuclear factor kappaB activation in both liver and tumor cells during initial stages of hepatic metastasis

Various factors involved in tumor metastasis are regulated by the transcription factor nuclear factor kappaB (NF-kappaB). Because NF-kappaB activation may contribute to establishment of hepatic metastasis, its activation in liver cells and tumor cells was separately evaluated in a mouse model of hepatic metastasis. pNF-kappaB-Luc, a firefly luciferase-expressing plasmid DNA depending on the NF-kappaB activity, was injected into the tail vein of mice by the hydrodynamics-based procedure, a well-established method for gene transfer to BALB/c male mouse liver. The luciferase activity in the liver was significantly increased by an intraportal inoculation of murine adenocarcinoma colon26 cells, but not of peritoneal macrophages, suggesting that the NF-kappaB in liver cells is activated when tumor cells enter the hepatic circulation. Then, colon26 cells stably transfected with pNF-kappaB-Luc were inoculated. The firefly luciferase activity, an indicator of NF-kappaB activity in tumor cells, was significantly increased when colon26/NFkappaB-Luc cells were inoculated into the portal vein of BALB/c male mice. The NF-kappaB activation in both liver and tumor cells was significantly inhibited by injection of catalase derivatives, which have been reported to inhibit hepatic metastasis of tumor cells. These findings indicate for the first time that NF-kappaB, a key agent regulating the expression of various molecules involved in tumor metastasis, is activated in both liver and tumor cells during the initial stages of tumor metastasis through a hydrogen peroxide mediated pathway. Thus, the removal of hydrogen peroxide will be a promising approach to treating hepatic metastasis.

Cationized catalase-loaded hydrogel for growth inhibition of peritoneally disseminated tumor cells

A previous study demonstrated that ethylenediamine-conjugated catalase (ED-catalase) inhibits peritoneal dissemination of tumor cells in mice. To increase its inhibitory effects by sustained release, a hydrogel formulation of ED-catalase was prepared using a biodegradable hydrogel consisting of an acidic gelatin with an isoelectric point of 5.0. Although intraperitoneally injected ED-catalase solution rapidly disappeared from the cavity, more than 10% of ED-catalase remained even at 14 days after implantation of ED-catalase/hydrogel into the cavity. Then, the effect of ED-catalase/hydrogel on peritoneal dissemination of tumor cells was evaluated by measuring the luciferase activity of abdominal organs after intraperitoneal inoculation of colon26/Luc, a colon adenocarcinoma stably expressing luciferase. ED-catalase/hydrogel showed a significantly (P<0.05) greater effect on inhibiting the growth of tumor cells than ED-catalase solution, demonstrating the importance of the retention of ED-catalase within the cavity as far as inhibition is concerned. Serial in vivo images of luciferase activity revealed that the ED-catalase/hydrogel significantly (P<0.05) retarded the growth rate of tumor cells. Survival of tumor-bearing mice supported the findings obtained with the luminescence-based analyses. These findings indicate that the sustained release of ED-catalase from hydrogels into the cavity is highly effective in inhibiting the growth of peritoneally disseminated tumor cells.

Inhibition of peritoneal dissemination of tumor cells by cationized catalase in mice

To inhibit peritoneal dissemination of tumor cells by destroying hydrogen peroxide, ethylenediamine-conjugated catalase (ED-catalase), a cationized derivative, was injected into the peritoneal cavity of mice. ED-catalase had about a 6-fold longer retention time within the cavity than unmodified catalase. Peritoneal dissemination was evaluated after intraperitoneal inoculation of B16-BL6/Luc, a melanoma clone stably expressing firefly luciferase, by measuring luciferase activity. An intraperitoneal injection of ED-catalase just before tumor inoculation significantly reduced the number of tumor cells in peritoneal organs. Catalase was less effective, confirming the importance of the retention of the enzyme within the cavity for the inhibition. ED-catalase injected 3 days after tumor inoculation was also effective in inhibiting tumor growth. A real-time quantitative PCR analysis revealed that ED-catalase significantly suppressed the expression of intercellular adhesion molecule-1. Daily dosing of ED-catalase for 7 days significantly prolonged the survival of tumor-bearing mice. These findings indicate that ED-catalase, which is retained for a long time within the peritoneal cavity, is highly effective in inhibiting the adhesion and proliferation of peritoneally disseminated tumor cells, and in increasing the survival of tumor-bearing mice.