GF-1 Cells Research Articles

ISKNV Triggers AMPK/mTOR-Mediated Autophagy Signaling through Oxidative Stress, Inducing Antioxidant Enzyme Expression and Enhancing Viral Replication in GF-1 Cells.

Infectious spleen and kidney necrosis virus (ISKNV) infections can induce the process of host cellular autophagy but have rarely been identified within the molecular autophagy signaling pathway. In the present study, we demonstrated that ISKNV induces ROS-mediated oxidative stress signals for the induction of 5'AMP-activated protein kinase/mechanistic target of rapamycin kinase (AMPK/mTOR)-mediated autophagy and upregulation of host antioxidant enzymes in fish GF-1 cells. We also examined ISKNV-induced oxidative stress, finding that reactive oxidative species (ROS) increased by 1.5-fold and 2.5-fold from day 2 to day 3, respectively, as assessed by the H2DCFDA assay for tracing hydrogen peroxide (H2O2), which was blocked by NAC treatment in fish GF-1 cells. Furthermore, ISKNV infection was shown to trigger oxidative stress/Nrf2 signaling from day 1 to day 3; this event was then correlated with the upregulation of antioxidant enzymes such as Cu/ZnSOD and MnSOD and was blocked by the antioxidant NAC. Using an MDC assay, TEM analysis and autophagy marker LC3-II/I ratio, we found that ROS stress can regulate autophagosome formation within the induction of autophagy, which was inhibited by NAC treatment in GF-1 cells. Through signal analysis, we found that AMPK/mTOR flux was modulated through inhibition of mTOR and activation of AMPK, indicating phosphorylation levels of mTOR Ser 2448 and AMPK Thr 172 from day 1 to day 3; however, this process was reversed by NAC treatment, which also caused a reduction in virus titer (TCID50%) of up to 1000 times by day 3 in GF-1 cells. Thus, ISKNV-induced oxidative stress signaling is blocked by antioxidant NAC, which can also either suppress mTOR/AMPK autophagic signals or reduce viral replication. These findings may provide the basis for the creation of DNA control and treatment strategies.

C-myc modulates the replication of RGNNV via glutamine-mediated ATP production in grouper fin cells

C-myc is a proto-oncogene that plays an important role in a variety of diseases. There were a lot of research on the correlation between C-myc and human viruses. However, the study about C-myc related to aquatic species virus is very limited. In the present study, the qRT-PCR, cellular immunofluorescence and western blotting determination data reported that C-myc and glutaminase (GLS) genes were significantly upregulated when grouper fin cells (GF-1) were infected with red grouper nervous necrosis virus (RGNNV). After knocking down the C-myc gene, the mRNA and protein levels of GLS, capsid protein (CP) and RNA polymerase (RdRp) of RGNNV were significantly reduced in RGNNV-infected GF-1 cells and the overexpression of the C-myc gene remarkably promoted these genes, which indicated that the replication of the virus and GLS gene were positively regulated by C-myc in RGNNV-infected GF-1 cells. In addition, supplementation of exogenous ATP can partially restore viral replication when RGNNV-infected GF-1 cells were cultured in glutamine-free medium, which confirmed that the glutamine was decomposed into ATP to provide energy for viral replication. Further studies confirmed that overexpression of C-myc can increase the content of ATP in normal cells. To sum up, these data suggested that activation of C-myc gene affected viral replication by regulating GLS expression to drive glutamine dissolution.

Characterization of Nervous Necrosis Virus (NNV) Nonstructural Protein B2 and Its Enhancement on Virus Proliferation.

The nerve necrosis virus (NNV), a pathogen of viral nervous necrosis disease in several important mariculture economic fish species, causes economic loss. Its nonstructural protein B2 encoded by the sub-genomic RNA3 affects the amplification of the virus. In this study, the B2 protein was recombinantly expressed, the polyclonal antibodies were produced and the dynamics of the B2 protein and genomes were measured in vivo and in vitro after NNV infection. Then, the effects of the overexpressed B2 protein on virus proliferation were investigated. The results showed that the polyclonal antibodies can recognize the B2 protein in both SSN-1 cells and the brain/eye of the grouper. The RNA3 expression significantly increased at 12 h and kept rising till the end of the experiment; it was 106.9 copies/μL at 120 h. The B2 protein could be first detected at 3 h post-infection, which was earlier than the capsid protein was first detected (12 h post-infection). The B2 protein can be detected in the brain, eye and heart on day 3 and the copy number of genomes reached a maximum at 6 d post-infection. There was a low expression of NNV genomes in the liver, spleen and kidney, and no virus was detected in the gill, stomach and intestine. In the meantime, the B2 protein was successfully expressed in GF-1 cells and significantly enhanced virus proliferation, which produced an earlier cytopathic effect and higher cell death rates after 3 d post-infection than the control. In conclusion, the B2 protein acts as an early expressed protein during virus replication and proliferation and is involved in the early infection of NNV. The results may provide insight into the early stage of virus infection and prevention of the disease.

Infectious spleen and kidney necrosis virus induces the reactive oxidative species/Nrf2-mediated oxidative stress response for the regulation of mitochondrion-mediated Bax/Bak cell death signals in GF-1 cells.

Infectious spleen and kidney necrosis virus (ISKNV) infections can trigger host cell death and are correlated with viral replication; however, they have rarely been considered in terms of the host organelle involvement. In the present study, we demonstrated that ISKNV triggered an oxidative stress signal in the Nrf2-mediated oxidative stress response and induced stress signals for Bax/Bak-mediated host cell death in fish GF-1 cells. The results showed that after ISKNV infection, the levels of reactive oxidative species (ROS) increased by 60–80% from day 3 to day 5, as assessed by an H2DCFDA assay for tracing hydrogen peroxide (H2O2), which was correlated with up to a one-fold change in the fish GF-1 cells. Furthermore, we found that ISKNV infection induced Nrf2-mediated ROS stress signals from D1 to D5, which were correlated with the upregulation of antioxidant enzymes, such as catalase, SOD1, and SOD2; these effects were blocked by the antioxidants GSH and NAC. By analyzing Nrf2-mediated ROS stress signals for cell death regulation via an apoptotic assay, we found that treatment with antioxidants reduced annexin-V-positive signals by 10% (GSH) to 15% (NAC); moreover, necrotic-positive signals were reduced by 6% (GSH) and 32% (NAC) at day 5 (D5) in GF-1 cells, as indicated by PI staining. Furthermore, we found that Nrf2-mediated ROS stress regulated mitochondrion-mediated Bax/Bak death signals at D3 and D5; this was effectively blocked by antioxidant treatment in the GF-1 cells, as demonstrated by a JC1 assay (ΔΨm) and western blot analysis. In addition, we found that downstream signals for caspase-9 and -3 activation were apparently blocked by antioxidant treatment at D3 and D5. Finally, we found that treatment with GSH and NAC reduced major capsid protein (MCP) expression and virus titer (TCID50%) by up to 15-fold at D5 in GF-1 cells. Thus, our data suggest that ISKNV can induce ROS production, which triggers Nrf2-mediated stress signals. Then, these stress signals can regulate mitochondrion-mediated Bax/Bak apoptotic signaling, which is connected to downstream caspase-9 and -3 activation. If ISKNV-induced Nrf2-mediated stress signaling is blocked, then the antioxidants GSH and NAC can also suppress apoptotic signals or reduce viral replication. These findings may provide insights into the control and treatment of double-stranded DNA viruses.

Cytotoxicity of 3D-printed, milled, and conventional oral splint resins to L929 cells and human gingival fibroblasts.

ObjectivesEvidence on the biocompatibility of three‐dimensional (3D)‐printed and milled resins for oral splints is limited. This in vitro study assessed the influence of the manufacturing method on the cytotoxicity of oral splint resins on L929 cells and human gingival fibroblasts (GF1).Materials and MethodsStandardized specimens of four 3D‐printed, two‐milled, one‐thermoformed, and one‐pressed splint resin were incubated with L929 and GF1 cells for 24 h. Immunofluorescence and WST‐8 assay were performed to evaluate cytotoxic effects. One‐way analysis of variance and Tukey's multiple comparison test were applied with the variables “splint resin” and “manufacturing method” (p < .05).ResultsImmunofluorescence showed attachment of L929 and GF1 cells to the splint resins. Irrespective of the manufacturing method, the WST‐8 assay revealed significant differences between splint resins for the viability of L929 and GF1 cells. L929 cells generally showed lower viability rates than GF1 cells. The evaluation of cell viability by the manufacturing method showed no significant differences between 3D printing, milling, and conventional methods.ConclusionsThe cytotoxic effects of 3D‐printed, milled, and conventional oral splint resins were similar, indicating minor influence of the manufacturing method on biocompatibility. Cytotoxicity of the resins was below a critical threshold in GF1 cells. The chemical composition might be more crucial than the manufacturing method for the biocompatibility of splint resins.

Infectious Spleen and Kidney Necrosis Virus (ISKNV) Triggers Mitochondria-Mediated Dynamic Interaction Signals via an Imbalance of Bax/Bak over Bcl-2/Bcl-xL in Fish Cells.

The molecular pathogenesis of infectious spleen and kidney necrosis virus (ISKNV) infections is important but has rarely been studied in connection to host organelle behavior. In the present study, we demonstrated that ISKNV can induce host cell death via a pro-apoptotic Bcl-2 and anti-apoptotic Bcl-2 family member imbalance in mitochondrial membrane potential (MMP or ΔΨm) regulation in GF-1 cells. The results of our study on ISKNV infection showed that it can induce host cell death by up to 80% at day 5 post-infection. Subsequently, in an apoptotic assay, ISKNV infection was seen to induce an increase in Annexin-V-positive signals by 20% and in propidium iodide (PI) staining-positive signals by up to 30% at day 5 (D5) in GF-1 cells. Then, through our studies on the mechanism of cell death in mitochondria function, we found that ISKNV can induce MMP loss by up to 58% and 78% at days 4 and 5 with a JC1 dye staining assay. Furthermore, we found that pro-apoptotic members Bax and Bak were upregulated from the early replication stage (day one) to the late stage (day 5), but the expression profiles were very dynamically different. On the other hand, by Western blotted analysis, the anti-apoptotic members Bcl-2 and Bcl-xL were upregulated very quickly at the same time from day one (two-fold) and continued to maintain this level at day five. Finally, we found that pro-apoptotic death signals strongly activated the downstream signals of caspase-9 and -3. Taken together, these results suggest that ISKNV infection can induce Bax/Bak-mediated cell death signaling downstream of caspase-9 and -3 activation. During the viral replication cycle with the cell death induction process, the anti-apoptotic members Bcl-2/Bcl-xL interacted with the pro-apoptotic members Bax/Bak to maintain the mitochondrial function in the dynamic interaction so as to maintain the MMP in GF-1 cells. These findings may provide insights into DNA-virus control and treatment.

Differential Nervous Necrosis Virus (NNV) Replication in Five Putative Susceptible Cell Lines.

Viral encephalopathy and retinopathy caused by nervous necrosis virus (NNV), is one of the most threatening viral diseases affecting marine fish worldwide. In vitro propagation of NNV strains is essential for the design of effective control measures. In the present study we analysed both the susceptibility and the permissiveness of five fish cell lines (E-11, GF-1, SAF-1, DLB-1, and SaB-1) to three NNV strains (one RGNNV, one SJNNV, and one reassortant RGNNV/SJNNV). E-11 and DLB-1 were demonstrated to be highly susceptible to NNV strains, with average adsorption efficiency (AE) values higher than 90%. SAF-1 also showed high susceptibility (AE 88%), whereas GF-1 can be regarded as moderately susceptible (AE around 50%). On the contrary, SaB-1 can be considered a poorly susceptible cell line (AE values below 20%). E-11 and GF-1 cell lines provided the highest production rates for RGNNV and RG/SJ (around 103) and both cell lines can be regarded as fully permissive for these viral types. However, the SJNNV production rate in GF-1 was only 17.8 and therefore this cell line should be considered semi-permissive for this genotype. In SAF-1 cells, moderate viral replication was recorded but differences in intracellular and extracellular production suggest that viral progeny was not efficiently released. In DLB-1 and SaB-1 the final viral titres obtained in E-11 were lower than those of the inoculum. However, RNA1 synthesis values seem to indicate that RGNNV replication in DLB-1 and SAF-1 could have been underestimated, probably due to a poor adaptation of the virus grown in these cell lines to E-11. Based on all these results, E-11 seems to be the most appropriate cell for in vitro culture of RGNNV, SJNNV, and reassortant strains.

Developing a Virus-Binding Bacterium Expressing Mx Protein on the Bacterial Surface to Prevent Grouper Nervous Necrosis Virus Infection.

Grouper nervous necrosis virus (GNNV) infection causes mass grouper mortality, leading to substantial economic loss in Taiwan. Traditional methods of controlling GNNV infections involve the challenge of controlling disinfectant doses; low doses are ineffective, whereas high doses may cause environmental damage. Identifying potential methods to safely control GNNV infection to prevent viral outbreaks is essential. We engineered a virus-binding bacterium expressing a myxovirus resistance (Mx) protein on its surface for GNNV removal from phosphate-buffered saline (PBS), thus increasing the survival of grouper fin (GF-1) cells. We fused the grouper Mx protein (which recognizes and binds to the coat protein of GNNV) to the C-terminus of outer membrane lipoprotein A (lpp-Mx) and to the N-terminus of a bacterial autotransporter adhesin (Mx-AIDA); these constructs were expressed on the surfaces of Escherichia coli BL21 (BL21/lpp-Mx and BL21/Mx-AIDA). We examined bacterial surface expression capacity and GNNV binding activity through enzyme-linked immunosorbent assay; we also evaluated the GNNV removal efficacy of the bacteria and viral cytotoxicity after bacterial adsorption treatment. Although both constructs were successfully expressed, only BL21/lpp-Mx exhibited GNNV binding activity; BL21/lpp-Mx cells removed GNNV and protected GF-1 cells from GNNV infection more efficiently. Moreover, salinity affected the GNNV removal efficacy of BL21/lpp-Mx. Thus, our GNNV-binding bacterium is an efficient microparticle for removing GNNV from 10‰ brackish water and for preventing GNNV infection in groupers.

Heterologous expression of bacterial CotA-laccase, characterization and its application for biodegradation of malachite green

Malachite green (MG) is used as fungicide/parasiticide in aquaculture, its persistence is detrimental as it exhibits carcinogenic effects to aquatic organisms. Bacterial laccase evaluated as the best enzyme at extreme condition for aquatic MG removal. Study aims to increase laccase concentration, CotA-laccase from Bacillus subtilis was cloned and overexpressed in Escherichia coli. Optimal catalysis for purified CotA-laccase were at pH 5.0, 60 °C, and 1 mM of (2,2-azino-di-[3-ethylbenzothiazoline-sulphonate-(6)]) with Km and Kcat 0.087 mM and 37.64 S-1 respectively. MG biodegradation by CotA-laccase in clam and tilapia pond wastewaters and cytotoxic effect of biodegraded products in grouper fin-1 cells were determined. MG degradation by CotA-laccase was equally efficient, exhibiting upto 90–94% decolorization at freshwater and saline conditions and treated solution was non-toxic to GF-1 cells. Thus, recombinant-CotA-laccase could be an environmentally-friendly enzyme for aquaculture to remove MG, thereby effective to reduce its accumulation in aquatic organisms and ensuring safe aquaculture products.

Ammonium produced from Shewanella strain 0409 contributes to antiviral activity against Betanodavirus

Nervous necrosis virus (NNV) (genus: Betanodavirus) attacks aquacultured fish. Biocontrol may prevent and control the disease caused by NNV infection. Shewanella strain 0409 was isolated from the microbiome of grouper intestines, and its culture supernatant (CS0409) could inhibit NNV replication in vitro. The present study elucidated the antiviral mechanism of Shewanella strain 0409 against NNV in vitro. In NNV-infected GF-1 cells, CS0409 reduced both NNV RNA synthesis and the percentage of cells expressing NNV RNA-dependent RNA polymerase (RdRp) within 24 hpi. However, NNV RdRp activity was not inhibited by CS0490 treatment. The most favorable time for CS0409 treatment in NNV-infected GF-1 cells was the period of viral adsorption, which revealed a high inhibition level of NNV RNA synthesis. Shewanella strain 0409 produced ammonium in CS0409. When ammonium in CS0409 was removed by heating with evaporation, the anti-NNV activity of CS0409 decreased. Moreover, ammonium in CS0409 inhibited the acidification of acidic organelles. Furthermore, the morphology of NNV virions changed to empty particles after exposure to pH 5 and 6, indicating that NNV uncoating required the acidic environment of endosomes. Therefore, ammonium in CS0409 is responsible for the anti-NNV activity in vitro by inhibiting the acidification of endosomes and then suppressing NNV uncoating.

Screening for the Proteins That Can Interact with Grouper Nervous Necrosis Virus Capsid Protein.

Nervous necrosis virus (NNV) can infect many species of fish and has an 80–100% mortality rate. NNV capsid protein (NNVCP) is the only structural protein of NNV, but there are few studies on the protein–protein interaction between NNVCP and the host cell. To investigate NNV morphogenesis, native NNV capsid protein (NNVCP) was used to screen for protein–protein interactions in this study. The results identified that 49 grouper optic nerve proteins can interact with NNVCP and may function as putative receptor or co-receptor, cytoskeleton, glucose metabolism and ATP generation, immunity, mitochondrial ion regulation, and ribosomal proteins. Creatine kinase B-type (CKB) is one of those 49 optic nerve proteins. CKB, a kind of enzyme of ATP generation, was confirmed to interact with NNVCP by far-Western blot and showed to colocalize with NNVCP in GF-1 cells. Compared to the control, the expression of CKB was significantly induced in the brain and eyes infected with NNV. Moreover, the amount of replication of NNV is relatively high in cells expressing CKB. In addition to providing the database of proteins that can interact with NNVCP for subsequent analysis, the results of this research also verified that CKB plays an important role in the morphogenesis of NNV.

First isolation and identification of red-grouper nervous necrosis virus (RGNNV) from adult hybrid Hulong grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) in China

With the sharp development of present aquaculture, outbreaks of viral diseases have become a major obstacle for the sustainable development of the aquaculture industry with massive economic losses. Viral encephalopathy and retinopathy (VER) represents one of the main viral threats to world aquaculture, which is caused by nervous necrosis virus (NNV). In the present study, a new RGNNV strain named RGNNV-HL was isolated from cultured adult hybrid Hulong grouper (Epinephelus fuscoguttatus(♀) × Epinephelus lanceolatus(♂)) in Guangdong province, China. Cell culture-based virus isolation, RT-PCR detection, tissue section, electron microscopy, and complete genome sequence were used for virus identification. Furthermore, an artificial infection experiment was conducted for virulence testing. Gross examination of affected fish showed no noticeable lesions, no parasites in the gills or on the body surfaces, and no pathogenic bacteria. Histopathological examination revealed severe vacuolations in the brain of diseased groupers. Inoculation of the tissue homogenates of diseased fish induced obvious cytopathic effects in SSN-1, GF-1, and GS cell cultures. Electron microscopic observation revealed the presence of small-sized icosahedral-shaped viral particles (~30 nm) with no viral envelope, similar to betanodaviruses. RT-PCR and sequencing analysis confirmed the presence of red-spotted grouper nervous necrosis virus (RGNNV) capsid protein sequences. The virus clustered with RGNNV genotype, genus Betanodavirus within the Nodaviridae family on an evolutionary tree constructed based on the complete genome sequence. Thus, this newly isolated virus from adult Hulong grouper is tentatively designated RGNNV-HL. The artificial infection experiment showed that groupers began to die at 4 and 5 days after intraperitoneal injection and bath immersion, respectively. The cumulative mortality rates by injection and bath were 90% and 83.33%, respectively. To the best of our acknowledge, this is the first report of the isolation and characterization of RGNNV from Hulong grouper. Findings from this study will provide a candidate material and useful epidemiology information for further study on the infection mechanism and prevention and control strategies for RGNNV.

Characterization of betanodavirus quasispecies influences on the subcellular localization and expression of tumor necrosis factor (TNF)

The aim of this study was to investigate the influence of variant coat proteins (CPs) from different quasispecies of betanodavirus on diverse aspects of nodavirus-induced pathogenesis. It is known that variant CPs can acquire either nuclear or cytoplasmic localization, depending on the nodavirus CP genotype, and this variation may arise during viral replication and influence the regulation of host and viral gene transcription. To investigate the role of these variant CPs in pathogenesis, six variant CP expression plasmids were constructed, each containing different quasispecies CP variants from nodavirus genotype red spotted grouper nervous necrosis virus (RGNNV). The CP expression plasmids were transiently transfected into grouper GF-1 cells. At different times, the cell cycle and cell proliferation were assayed using flow cytometry and methyl thiazolyl tetrazolium (MTT) assays, respectively. The proportion of G2/M-phase GF-1 cells transfected with CP expression plasmids was higher than that of cells transfected with the blank plasmid, especially in regards to quasispecies 2 (QS2). The proliferation ratio of cells transfected with the CP expression plasmids was significantly higher than that of cells transfected with the blank plasmid, with the exception of QS6. We also found that the different quasispecies CPs downregulated the promoter activity of the tumor necrosis factor (TNF) gene to different degrees. In addition, this is the first report showing the betanodavirus CP derived from different quasispecies of RGNNV provide evidence of a chronically nodavirus-infected grouper. Overall, this study represents the first comprehensive analysis of variant CPs from grouper with persistent nodavirus infections and their effects on different aspects of pathogenesis.

The presence of substances of the Shewanella strain 0409, isolated from grouper intestine, gives antiviral activity against Betanodavirus in cell cultures and protection of fish

Nervous necrosis virus (NNV), belonging to the genus Betanodavirus, causes mass mortality of many species of marine and freshwater fish at the larval and juvenile stages. Biocontrol is a potential strategy for the prevention and control of diseases associated with NNV infection. A bacterial strain, 0409, was isolated from the microbiome of grouper intestines, and the bacterial culture supernatant (CS0409) was found to suppress NNV RNA synthesis and reduce NNV titers. The aim of the present study was to elucidate how the bacterial strain 0409 antagonized NNV in vitro and in vivo. The 16S rDNA of strain 0409 had high sequence identity to Shewanella spp. The anti-NNV substances in CS0409 were heat stable, resistant to protease and nuclease activity, widely pH-tolerant, hydrophilic, and had molecular weights of <3 kDa. CS0409 exhibited anti-NNV effects, but not by neutralizing NNV or blocking the viral receptor on GF-1 cells. The anti-NNV activity of CS0409 was present when NNV-infected GF-1 cells were treated with CS0409 prior to 2 h post infection (hpi) and had to be cultured in CS0409-supplemented medium throughout the entire course of the experiment. Once CS0409 was removed from the culture medium of infected cells, the anti-NNV effect was abrogated. Moreover, CS0409 could induce cBB cells to express Mx gene, which could inhibit NNV RNA synthesis. Furthermore, groupers that were fed with strain 0409 for 2 months showed lower morbidity and mortality after NNV challenge compared with the mock-fed groupers. Therefore, strain 0409 has the potential to be a beneficial bacterium for biocontrol against NNV.

EPA and DHA can modulate cell death via inhibition of the Fas/tBid-mediated signaling pathway with ISKNV infection in grouper fin cell line (GF-1) cells

Polyunsaturated fatty acids (PUFAs) play important roles in organisms, including the structure and liquidity of cell membranes, anti-oxidation and anti-inflammation. Very little has been done in terms of the effect of PUFAs on cell death, especially on DNA virus. In this study, we demonstrated that the infectious spleen and kidney necrosis virus (ISKNV) can induce host cell death via the apoptotic cell death pathway, which correlated to modulation by PUFAs in grouper fin cell line (GF-1) cells. We screened the PUFAs, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for the ability of different dosages to prevent cell death in GF-1 cells with ISKNV infection. In the results, each 10 μM of DHA and EPA treatment enhanced host cell viability up to 80% at day 5 post-infection. Then, in Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) assay, DHA- and EPA-treated groups reduced TUNEL positive signals 50% in GF-1 cells with ISKNV infection. Then, through studies of the mechanism of cell death, we found that ISKNV can induce both the Bax/caspase-3 and Fas/caspase-8/tBid death signaling pathways in GF-1 cells, especially at day 5 post-infection. Furthermore, we found that DHA and EPA treatment can either prevent caspase-3 activation on 17-kDa form cleavage or Bid cleaved (15-kDa form) for activation by caspase-8, apparently. On the other hand, the anti-apoptotic gene Bcl-2 was upregulated 0.3-fold and 0.15-fold at day 3 and day 5, respectively, compared to ISKNV-infected and DHA-treated cells; that this did not happen in the EPA-treated group showed that different PUFAs trigger different signals. Finally, ISKNV-infected GF-1 cells treated with either DHA or EPA showed a 5-fold difference in viral titer at day 5. Taken together, these results suggest that optimal PUFA treatment can affect cell death signaling through both the intrinsic and extrinsic death pathways, reducing viral expression and viral titer in GF-1 cells. This finding may provide insight in DNA virus infection and control.

Inhibition of Cyclophilin A on the replication of red spotted grouper nervous necrosis virus associates with multiple pro-inflammatory factors

Cyclophilin A (CypA) is a ubiquitously expressed cellular protein and involves in diverse pathological conditions, including infection and inflammation. CypA acts as a key factor in the replication of several viruses. However, little is known about the role of CypA in the replication of the red-spotted grouper nervous necrosis virus (RGNNV). In the present report, grouper CypA (GF-CypA) was cloned from the grouper fin cell line (GF-1) derived from orange-spotted grouper (Epinephelus coioides). Sequence analysis found that GF-CypA open reading frame (ORF) of 495 bp encodes a polypeptide of 164 amino acids residues with a molecular weight of 17.4 kDa. The deduced amino acid sequence shared highly conserved regions with CypA of other animal species, showing that GF-CypA is a new member of Cyclophilin A family. We observed that GF-CypA was up-regulated in the GF-1 cells infected with RGNNV. Additionally, overexpression of CypA could significantly inhibit the replication of RGNNV in GF-1 cells. By contrast, when the GF-CypA was knock-downed by siRNA in GF-1 cells, the replication of RGNNV was enhanced. Furthermore, the expressions of pro-inflammatory factors, such as TNF-2, TNF-α, IL-1b, and ISG-15, were increased in GF-CypA transfected GF-1 cells challenged with RGNNV, indicating that GF-CypA might be involved in the regulation of the host pro-inflammatory factors. Altogether, we conclude that GF-CypA plays a vital role in the inhibitory effect of RGNNV replication that might be modulating the cytokines secretion in GF-1 cells during RGNNV infection. These results will shed new light on the function of CypA in the replication of RGNNV and will pave a new way for the prevention of the infection of RGNNV in fish.

Nuclear targeting of the betanodavirus B1 protein via two arginine-rich domains induces G1/S cell cycle arrest mediated by upregulation of p53/p21

The molecular functions of betanodavirus non-structural protein B and its role in host cell survival remain unclear. In the present study, we examined the roles of specific nuclear targeting domains in B1 localization as well as the effect of B1 nuclear localization on the cell cycle and host cell survival. The B1 protein of the Red spotted grouper nervous necrosis virus (RGNNV) was detected in GF-1 grouper cells as early as 24 hours post-infection (hpi). Using an EYFP-B1 fusion construct, we observed nuclear localization of the B1 protein (up to 99%) in GF-1 cells at 48 hpi. The nuclear localization of B1 was mediated by two arginine-rich nuclear targeting domains (B domain: 46RRSRR51; C domain: 63RDKRPRR70) and domain C was more important than domain B in this process. B1 nuclear localization correlated with upregulation of p53 and p21(wef1/cip1); downregulation of Cyclin D1, CDK4 and Mdm2; and G1/S cell cycle arrest in GF-1 cells. In conclusion, nuclear targeting of the RGNNV B1 protein via two targeting domains causes cell cycle arrest by up-regulating p53/p21 and down-regulating Mdm2, thereby regulating host cell survival.

Abstract 5162: Oligodendrocytes might up-regulate the invasiveness of glioblastoma cells via Angiopoietin-2 signaling pathway

Abstract Background &amp; Aims: Glioblastoma (GBM, WHO Grade IV) is considered as the most lethal neoplasm of all solid cancers due to its inherent intensive invasiveness. GBM may arise de novo, or following progression from lower grade gliomas. Recently, solid tumor progression has been recognized as the product of an evolving crosstalk between the cancer cells and its surrounding glial cells. The intensive invasion activity of GBM cells might be regulated by surrounding normal cells such as oligodendrocytes or fibroblasts. In this study, we evaluated the interactive factors between GBM cells and normal glial cells to determine the role of oligodendrocytes in regulating the invasiveness of glioblastoma cells. Methods: Two GBM cell lines, T98G and U251, were used. Two oligodendrocyte cell lines, ODC1 and ODC2, were derived one each from surgical tissues of patients with low-grade glioma (WHO Grade II). Two fibroblasts cell lines, GF1 and GF2, were derived one each from surgical tissues of patients with GBM. Oligodendrocytes and fibroblasts were confirmed by immuno-histochemical staining. The invasive property of GBM cells was analyzed in the presence or absence of conditioned medium from oligodendrocytes or fibroblasts by wound-healing assay and Boyden chamber invasion assay. The proliferation ability of GBM cells was examined by MTT assay. Subsequently Cytokine array was used to examine the cytokines and growth factors in the conditioned medium from oligodendrocytes or fibroblasts. Results: Oligodendrocyte cells, ODC1 and ODC2 cells, significantly (p&amp;lt;0.01) increased the migration and invasion ability of GBM cells, T98G and U251. In contrast, fibroblasts, GF1 and GF2 cells, did not affect the migration and invasion ability of GBM cells. Cytokine array indicated that Angiopoietin-2 was found in the conditioned medium from oligodendrocytes, but not that from fibroblasts. Angiopoietin-2 significantly (p&amp;lt;0.01) increased the invasiveness of GBM, but not their proliferation ability. Conclusion: Oligodendrocytes might up-regulation of the invasiveness of GBM cells via angiopoietin-2 signaling pathway. Hence, angiopoietin-2 can be considered as a promising target for the treatment of malignant gliomas. Citation Format: Toshiyuki Kawashima. Oligodendrocytes might up-regulate the invasiveness of glioblastoma cells via Angiopoietin-2 signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5162.

Abstract 945: Oligodendrocytes might up-regulate the Invasiveness of glioblastoma cells via angiopoietin-2 signaling

Abstract Background &amp; Aims: Glioblastoma (GBM, WHO Grade IV) is considered as the most lethal neoplasm of all solid cancers due to its inherent intensive invasiveness. GBM may arise de novo, or following progression from lower grade gliomas. Recently, solid tumor progression has been recognized as the product of an evolving crosstalk between the cancer cells and its surrounding glial cells. The intensive invasion activity of GBM cells might be regulated by surrounding normal cells such as oligodendrocytes or fibroblasts. In this study, we evaluated the interactive factors between GBM cells and normal glial cells to determine the role of oligodendrocytes in regulating the invasiveness of glioblastoma cells. Methods: Two GBM cell lines, T98G and U251, were used. Two oligodendrocyte cell lines, ODC1 and ODC2, were derived one each from surgical tissues of patients with low-grade glioma (WHO Grade II). Two fibroblasts cell lines, GF1 and GF2, were derived one each from surgical tissues of patients with GBM. Oligodendrocytes and fibroblasts were confirmed by immuno-histochemical staining. The invasive property of GBM cells was analyzed in the presence or absence of conditioned medium from oligodendrocytes or fibroblasts by wound-healing assay and Boyden chamber invasion assay. The proliferation ability of GBM cells was examined by MTT assay. Subsequently Cytokine array was used to examine the cytokines and growth factors in the conditioned medium from oligodendrocytes or fibroblasts. Results: Oligodendrocyte cells, ODC1 and ODC2 cells, significantly (p&amp;lt;0.01) increased the migration and invasion ability of GBM cells, T98G and U251. In contrast, fibroblasts, GF1 and GF2 cells, did not affect the migration and invasion ability of GBM cells. Cytokine array indicated that Angiopoietin-2 was found in the conditioned medium from oligodendrocytes, but not that from fibroblasts. Angiopoietin-2 significantly (p&amp;lt;0.01) increased the invasiveness of GBM, but not their proliferation ability. Conclusion: Oligodendrocytes might up-regulation of the invasiveness of GBM cells via angiopoietin-2 signaling pathway. Hence, angiopoietin-2 can be considered as a promising target for the treatment of malignant gliomas. Citation Format: Toshiyuki Kawashima. Oligodendrocytes might up-regulate the Invasiveness of glioblastoma cells via angiopoietin-2 signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 945. doi:10.1158/1538-7445.AM2017-945

Anti-apoptotic genes Bcl-2 and Bcl-xL overexpression can block iridovirus serine/threonine kinase-induced Bax/mitochondria-mediated cell death in GF-1 cells

Although serine/threonine (ST) kinase is known to induce host cell death in GF-1 cells, it remains unclear how ST kinase induces mitochondrial function loss. In the present study, we addressed the issue of mitochondrial function loss by determining whether the Bcl-2 family members Bcl-2 and Bcl-xL can prevent ST kinase-induced cell death activity via interacting with the pro-apoptotic gene Bax. Grouper fin cells (GF-1) carrying EGFP-Bal-xL and EGFP-Bcl-2 fused genes were selected, established in cell culture, and used to examine the involvement of Bcl-2 and Bcl-xL overexpression in protection of GF-1 cells from the effects of the giant sea perch iridovirus (GSIV) ST kinase gene. Using the TUNEL assay, we found that EGFP-Bcl-2 and EGFP-Bcl-xL reduced GSIV ST kinase-induced apoptosis to 20% all at 24 h and 48 h post-transfection (pt). Also, Bcl-2 and Bcl-xL substantially reduced the percentage of cells with GSIV ST kinase-induced loss of mitochondrial membrane potential (Δψps) at 24 and 48 hpt, respectively, and this reduction correlated with a 30% and 50% enhancement of host cell viability at 24 and 48 hpt as compared with vector control. Moreover, analysis of the effect of Bcl-2 and Bcl-xL interaction with Bax targeted to mitochondria during ST kinase expression at 48 hpt found that Bcl-2 and Bcl-xL also interacted with Bax to block cytochrome c release. Finally, Bcl-2 and Bcl-xL overexpression caused blockage of ST kinase function at 48 hpt, which was correlated with preventing caspase-9 and -3 cleavage and activation, thereby blocking downstream death signaling events. Taken together, our results suggest that the ST kinase-induced Bax/mitochondria-mediated cell death pathway can be blocked by the interaction of Bcl-2 and Bcl-xL with Bax to inhibit cytochrome c release during MMP loss. This rescue activity also correlated with inhibition of caspase-9 and -3 activation, thereby enhancing cell viability.