Autophagy induced by largemouth bass virus inhibits virus replication and apoptosis in epithelioma papulosum cyprini cells

Study of the antivirus function mediated by STING in Micropterus salmoides

Stimulator of interferon genes (STING) has been demonstrated as a critical mediator in the innate immune response to cytosolic DNA and RNA derived from different pathogens. While the role of Micropterus salmoides STING (MsSTING) in largemouth bass virus is still unknown. In this study, RT-qPCR assay and Western-blot assay showed that the expression levels of MsSTING and its downstream genes were up-regulated after LMBV infection. Pull down experiment proved that a small peptide called Fusion peptide (FP) that previously reported to target to marine and human STING as a selective inhibitor also interacted with MsSTING in vitro. Comparing with the RNA-seq of Largemouth bass infected with LMBV singly, 326 genes were significantly up-regulated and 379 genes were significantly down-regulated in the FP plus LMBV group in which Largemouth bass was treatment with FP before LMBV-challenged. KEGG analysis indicated that the differentially expressed genes (DEGs) were mainly related to signaling transduction, infectious disease viral, immune system and endocrine system. Besides, the survival rate of LMBV-infected largemouth bass was highly decreased following FP treatment. Taken together, our study showed that MsSTING played an important role in immune response against LMBV infection.

Green tea polyphenols inhibit TBBPA-induced lung injury via enhancing antioxidant capacity and modulating the NF-κB pathway in mice

Tetrabromobisphenol A (TBBPA) is a global pollutant. When TBBPA is absorbed by the body through various routes, it can have a wide range of harmful effects on the body. Green tea polyphenols (GTPs) can act as antioxidants, resisting the toxic effects of TBBPA on animals. The effects and mechanisms of GTP and TBBPA on oxidative stress, inflammation and apoptosis in the mouse lung are unknown. Therefore, we established in vivo and in vitro models of TBBPA exposure and GTP antagonism using C57 mice and A549 cells and examined the expression of factors related to oxidative stress, autophagy, inflammation and apoptosis. The results of the study showed that the increase in reactive oxygen species (ROS) levels after TBBPA exposure decreased the expression of autophagy-related factors Beclin1, LC3-II, ATG3, ATG5, ATG7 and ATG12 and increased the expression of p62; oxidative stress inhibits autophagy levels. The increased expression of the pro-inflammatory factors IL-1β, IL-6 and TNF-α decreased the expression of the anti-inflammatory factor IL-10 and activation of the NF-κB p65/TNF-α pathway. The increased expression of Bax, caspase-3, caspase-7 and caspase-9 and the decreased expression of Bcl-2 activate apoptosis-related pathways. The addition of GTP attenuated oxidative stress levels, restored autophagy inhibition and reduced the inflammation and apoptosis levels. Our results suggest that GTP can attenuate the toxic effects of TBBPA by modulating ROS, reducing oxidative stress levels, increasing autophagy and attenuating inflammation and apoptosis in mouse lung and A549 cells. These results provide fundamental information for exploring the antioxidant mechanism of GTP and further for studying the toxic effects of TBBPA.

miR-193b-5p promotes GCRV replication by inhibiting autophagy via targeting deptor in grass carp (Ctenopharyngodon idellus)

miRNAs are increasingly recognized for their crucial role in autophagy processes. Recent research has highlighted the significant function of autophagy in modulating immune responses. Within this context, specific miRNAs have been identified as indirect mediators of immune functions through their modulation of autophagy. In this study, we verified that miR-193b-5p simultaneously targeted the grass carp autophagy-related gene deptor, thereby reducing autophagy levels in CIK cells. Moreover, we found the expression levels of miR-193b-5p and deptor responding to pathogen infections in the GCRV-infected CIK cells. Notably, the overexpression of miR-193b-5p was found to induce the GCRV replication and reduce the irf3, irf7 and IFN1 expression. These findings also demonstrated that grass carp miR-193b-5p impacted the proliferation, migration, and antiapoptotic abilities of CIK cells. All the above results indicated that miR-193b-5p was linked to grass carp autophagy and played a vital role in antiviral immunity by targeting deptor. Our study may provide important insights into autophagy-related miRNAs and their roles in defense and immune mechanisms against pathogens in teleost.

Comparative proteomic analysis of the protein profile in the cuttlefish Sepia pharaonis associated with skin ulceration syndrome

Skin ulceration syndrome (SUS) is becoming a severe problem in the breeding and culturing process of the cuttlefish Sepia pharaonis. However, limited knowledge is available about the occurrence of this devastating disease. In this study, proteomic analysis was used to identify the differentially expressed proteins (DEPs) and the biological pathways enriched in SUS-diseased S. pharaonis. Both the healthy group and diseased group were analyzed in triplicate, with 4 cuttlefish in each replicate. The results showed that 85 DEPs were identified between the two groups, including 36 upregulated proteins and 49 downregulated proteins in the diseased group compared to the healthy group. GO enrichment analysis revealed that the DEPs were mainly enriched in cellular component organization or biogenesis, nucleus and ion binding processes. The results of the KEGG pathway analysis indicated that extracellular matrix (ECM)-receptor interaction was the most enriched upregulated pathway. Real-time reverse transcriptase PCR was used to identify the expression of two differentially expressed matrix metalloproteinases (MMPs), and the results showed that the mRNA expression of MMP14 and MMP19 was significantly upregulated in the skin tissue of the diseased group. Furthermore, the protease activity of the diseased group was higher than that of the healthy group. Our results offer basic knowledge on the changes in protein profiles during the occurrence of SUS in the cuttlefish S. pharaonis.

Vitamin D3 can effectively and rapidly clear largemouth bass ranavirus by immunoregulation

Largemouth bass ranavirus (LMBV) is a highly destructive pathogen that causes significant mortality rates among largemouth bass populations. Unfortunately, there is a dearth of drug development efforts specifically aimed at treating LMBV. To address this, our study sought to investigate the potential effectiveness of incorporating varying doses of VD3 into the diet as a treatment for LMBV. Through qRT-PCR and semi-qPCR, we observed significant suppression and clearance of LMBV pathogens in largemouth bass fed with 15000 IU/Kg and 20000 IU/Kg of VD3 within 14 days. In addition, VD3 treatment significantly increased the expression levels of key immune-related genes such as IL-1β, IFN-γ, Mx, and IgM. Encouragingly, we observed that VD3 significantly increased antioxidant and immune activities such as TSOD, TAOC and C3 in serum and maintained total protein levels. Additionally, tissue pathology sections highlighted a dose-dependent relationship between VD3 supplementation and tissue damage, with the 15000 IU and 20000 IU groups exhibiting minimal damage. In conclusion, a reasonable concentration of VD3 effectively reduced LMBV replication and tissue damages, while improved immune-related genes expression and serum biochemical indices. These findings declare the considerable therapeutic potential of VD3 supplementation for combating LMBV disease and provide an alternative treatment option for fish farming.

Adamantoyl chloride inhibited replication of the largemouth bass virus via enhanced immunity and inhibition of apoptosis

The largemouth bass virus (LMBV) is a commonly encountered pathogen in aquaculture and presents significant challenges to development of the largemouth bass industry due to the lack of effective treatment methods. Here, the inhibitory potential and underlying mechanisms of adamantoyl chloride (AdCl) against LMBV were assessed both in vitro and in vivo. The results showed that AdCl (IC50 = 72.35 μM) significantly inhibited replication of LMBV in epithelioma papulosum cyprini (EPC) cells. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide and cytopathic effect (CPE) assays confirmed that AdCl inhibited replication of LMBV in EPC cells and significantly reduced the CPE effect, respectively. As a potential mechanism, AdCl inhibited apoptosis as determined by fluorescence and transmission electron microscopy. The results of flow cytometry showed that the apoptosis rate was decreased by 69 % in the AdCl-treated group as compared to the LMBV-infected group. Additionally, AdCl inhibited viral release. In vivo, the survival rate was 16.2 % higher in the AdCl-treated group as compared to the LMBV-infected group (26.9 % vs. 10.7 %, respectively). Additionally, the results of quantitative reverse transcription polymerase chain reaction (RT-qPCR) showed that AdCl significantly reduced the viral load of the fish liver, spleen, and kidneys at 3, 6, and 9 days postinfection. In addition, RT-qPCR analysis found that AdCl upregulated expression of immune-related genes to suppress replication of LMBV. Collectively, these results confirmed the anti-LMBV activities of AdCl for use in the aquaculture industry.

Integrated analysis of a miRNA-mRNA network related to immunity and autophagy in Macrobrachium rosenbergii infected with Aeromonas hydrophila

MicroRNAs (miRNAs) are a group of RNAs that regulate gene expression in the post-transcriptionally. miRNAs can regulate numerous processes, such as the immune response, due to their dynamic expression patterns. The giant freshwater prawn Macrobrachium rosenbergii is a major freshwater aquaculture prawn that is attacked by various bacteria, including Aeromonas hydrophila. For this study, we performed an analysis of the miRNA and mRNA transcriptome analysis of M. rosenbergii which was infected with A. hydrophila. We identified 56 differentially expressed miRNAs (DEMs) and 1542 differentially expressed mRNAs. Furthermore, an integrated analysis of miRNA-mRNA expression led to the identification of 729 differentially predicted target genes (DETGs) of the DEMs. Multiple functional categories related to immunity, apoptosis, and autophagy were found to be enriched in the DETGs. During the infection of M. rosenbergii by A. hydrophila, an elaborate regulatory network involving Toll and immune deficiency (IMD) signaling, mitogen-activated protein kinase (MAPK) signaling, lysosome, and cell apoptosis was formed by a complex interplay of 40 crucial DEMs and 22 DETGs, all associated with the immune and autophagy pathway. The findings suggest that infection with A. hydrophila triggers intricate responses in both miRNA and mRNA, significantly impacting immune and autophagy processes in M. rosenbergii.

Transcriptome analysis reveals the host immune response upon LMBV infection in largemouth bass (Micropterus salmoides)

Largemouth bass (Micropterus salmoides) is one of the important economical freshwater aquaculture species in China. However, the outbreak of viral diseases always caused great economic losses in the largemouth bass aquaculture industry. Largemouth bass virus (LMBV), a double-stranded DNA (dsDNA) virus belonging to genus Ranavirus, family Iridoviridae causes high mortality in cultivated largemouth bass. However, host responses, especially the molecular events involved in LMBV infection still remained largely uncertain. Here, we established an in vivo model of LMBV infection, and systematically investigated the mRNA expression profiles of host genes in liver and spleen from infected largemouth bass using RNA sequencing (RNA-seq). Histopathological analysis indicated that necrotic cells and the formed necrotic focus were present in spleen, while numerous basophilic cells, hepatocytes volume shrinkage, nucleus pyknosis, and the disappeared boundary of hepatocytes were observed in the liver of infected largemouth bass. Transcriptomic analysis showed that transcription levels of 5128 genes (2804 up-regulated genes and 2324 down-regulated) in liver and 7008 genes (2603 up-regulated and 4405 down-regulated) in spleen were altered significantly. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that numerous co-regulated differentially expressed genes (DEGs) in liver and spleen were enriched in the pathways related to cell death and immune signaling, such as apoptosis, necroptosis, cytokine-cytokine receptor interaction and JAK-STAT signaling. Moreover, the DEGs specially regulated by LMBV infection in liver were significantly enriched in the KEGG pathways related to metabolism and cell death, while those in spleen were enriched in the immune related pathways. In addition, the expression changes of several randomly selected genes, such as SOCS1, IL-6, CXCL2, CASP8, CYC and TNF from qPCR were consistent with the transcriptomic data. Taken together, our findings will provide new insights into the fundamental patterns of molecular responses induced by LMBV in vivo, but also contribute greatly to understanding the host defense mechanisms against iridoviral pathogens.

Isolation, identification and the pathogenicity characterization of a Santee-Cooper ranavirus and its activation on immune responses in juvenile largemouth bass (Micropterus salmoides)

The largemouth bass virus (LMBV) isolate of Santee-Cooper ranavirus showed evidence of widespread infection in adult fish, but disease presentation caused by different viral strains exhibited considerable difference. In this study, a highly pathogenic LMBV-like resembling Santee-Cooper ranavirus was isolated and identified from juvenile largemouth bass. The pathogenicity and dynamic distribution of LMBV-like strain, histopathological analysis and host immune response of juvenile largemouth bass infected with LMBV-like were investigated. The results show that LMBV-like was highly pathogenic to juvenile fish, and the infected fish showed typical signs of acute haemorrhages and visceral enlargement. LMBV-like positive cells were found in the liver, spleen, kidney, gills, and intestinal tissue, and the virus content in spleen was the highest. Histopathological analysis showed different pathological changes in major tissues of diseased fish, mostly manifested as infiltration of inflammatory cell and histiocyte necrosis. In addition, humoral immune factors such as superoxide dismutase (SOD), catalase (CAT) and acid phosphatase (ACP) were used as serum indicators to evaluate the immune response of juvenile fish after infection. Quantitative real-time PCR (qRT-PCR) was used to evaluate the expression patterns of immune-related genes (CD40, IFN-γ, IgM, IL-1β, IL-8, IL-12a, Mxd3, TGF-β, and TNFα) in liver, spleen, and head kidney tissues. The results showed that immunological activity of the juvenile largemouth bass was significantly enhanced by LMBV-like infection. This research comprehensively systematically revealed the pathogenic characteristics of LMBV-like separated from juvenile largemouth bass and properties of the host's immune response caused by the virus infection, which providing a basis for further exploring the interaction between the virus and the host, and prevention and treatment of disease caused by Santee-Cooper ranavirus.

Largemouth Bass Virus Infection Induced Non-Apoptotic Cell Death in MsF Cells

Largemouth bass virus (LMBV), belonging to the genus Ranavirus, causes high mortality and heavy economic losses in largemouth bass aquaculture. In the present study, a novel cell line, designated as MsF, was established from the fin of largemouth bass (Micropterus salmoides), and applied to investigate the characteristics of cell death induced by LMBV. MsF cells showed susceptibility to LMBV, evidenced by the occurrence of a cytopathic effect (CPE), increased viral gene transcription, protein synthesis, and viral titers. In LMBV-infected MsF cells, two or more virus assembly sites were observed around the nucleus. Notably, no apoptotic bodies occurred in LMBV-infected MsF cells after nucleus staining, suggesting that cell death induced by LMBV in host cells was distinct from apoptosis. Consistently, DNA fragmentation was not detected in LMBV-infected MsF cells. Furthermore, only caspase-8 and caspase-3 were significantly activated in LMBV-infected MsF cells, suggesting that caspases were involved in non-apoptotic cell death induced by LMBV in host cells. In addition, the disruption of the mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) generation were detected in both LMBV-infected MsF cells and fathead minnow (FHM) cells. Combined with our previous study, we propose that cell death induced by LMBV infection was cell type dependent. Although LMBV-infected MsF cells showed the characteristics of non-apoptotic cell death, the signal pathways might crosstalk and interconnect between apoptosis and other PCD during LMBV infection. Together, our results not only established the in vitro LMBV infection model for the study of the interaction between LMBV and host cells but also shed new insights into the mechanisms of ranavirus pathogenesis.