Transgenic expression of omega-3 PUFA synthesis genes improves zebrafish survival during Vibrio vulnificus infection

Does a High Ratio of Dietary Omega-6/Omega-3 Fatty Acids Increase the Risk of Helicobacter pylori Infection? A Case-Control Study

Helicobacter pylori infection is the cause of 90% of non-cardia gastric cancer. Several dietary elements have been identified as possible contributors to H. pylori infection and its advancement through various pathways. Based on the anti-inflammatory and anti-microbial effects of a diet low in omega-6 and high in omega-3 polyunsaturated fatty acids (PUFAs), this study aimed to assess the ratio of dietary omega-6 to omega-3 PUFAs and the risk of developing H. pylori. The present case-control study was conducted on 150 cases with H. pylori infection and 302 controls. The omega-6 to omega-3 ratio was calculated using food intake information sourced from a validated food frequency questionnaire. Physical activity and demographic data were collected through a related questionnaire. The association between the odds of H. pylori infection and the omega-6 to omega-3 ratio was evaluated using logistic regression models. A p value < 0.05 was considered statistically significant. The findings revealed that individuals in the third tertile had significantly higher odds of H. pylori (odds ratio [OR], 2.10; 95% confidence interval [CI], 1.30-3.40) in the crude model. Furthermore, even after adjusting the potential confounders including sex, age, body mass index, physical activity, energy intake, alcohol, and smoking status, this association remained significant (fully adjusted model: OR, 2.00; 95% CI, 1.17-3.34). Our study revealed a higher ratio of omega-6 to omega-3 was related to a higher likelihood of H. pylori infection. Therefore, it is advisable to maintain a balanced intake of PUFAs in the diet.

Zebrafish-based platform for emerging bio-contaminants and virus inactivation research

Emerging bio-contaminants such as viruses have affected health and environment settings of every country. Viruses are the minuscule entities resulting in severe contagious diseases like SARS, MERS, Ebola, and avian influenza. Recent epidemic like the SARS-CoV-2, the virus has undergone mutations strengthen them and allowing to escape from the remedies. Comprehensive knowledge of viruses is essential for the development of targeted therapeutic and vaccination treatments. Animal models mimicking human biology like non-human primates, rats, mice, and rabbits offer competitive advantage to assess risk of viral infections, chemical toxins, nanoparticles, and microbes. However, their economic maintenance has always been an issue. Furthermore, the redundancy of experimental results due to aforementioned aspects is also in examine. Hence, exploration for the alternative animal models is crucial for risk assessments. The current review examines zebrafish traits and explores the possibilities to monitor emerging bio-contaminants. Additionally, a comprehensive picture of the bio contaminant and virus particle invasion and abatement mechanisms in zebrafish and human cells is presented. Moreover, a zebrafish model to investigate the emerging viruses such as coronaviridae and poxviridae has been suggested.

Impacts of Fortifying Nile Tilapia (Oreochromis niloticus) Diet with Different Strains of Microalgae on Its Performance, Fillet Quality and Disease Resistance to Aeromonas hydrophila Considering the Interplay between Antioxidant and Inflammatory Response

The oxidative stress facing fish during intensive production brings about diseases and mortalities that negatively influence their performance. Along with that, the increased awareness of omega-3 polyunsaturated fatty acids (omega-3-PUFAs) health benefits has been triggered the introduction of alternative additives in aqua feed that cause not only modulation in fish immune response but also fortification of their fillet. In this context, the role of microalgae mix (NSS) containing Nannochloropsis oculate and Schizochytrium and Spirulina species, which were enriched with bioactive molecules, especially EPA and DHA, was assessed on Nile tilapia's performance, fillet antioxidant stability, immune response, and disease resistance. Varying levels of NSS (0.75, 1.5, and 3%) were added to Nile tilapia's diet for 12 weeks and then a challenge of fish with virulent Aeromonas hydrophila (A. hydrophila) was carried out. Results showed that groups fed NSS, especially at higher levels, showed an improved WG and FCR, which corresponded with enhanced digestive enzymes' activities. Higher T-AOC was detected in muscle tissues of NSS3.0% fed fish with remarkable reduction in ROS, H2O2, and MDA contents, which came in parallel with upregulation of GSH-Px, CAT, and SOD genes. Notably, the contents of EPA and DHA in fillet were significantly increased with increasing the NSS levels. The mean log10 counts of pathogenic Vibrio and Staphylococcus species were reduced, and conversely, the populations of beneficial Lactobacillus and Bacillus species were increased more eminent after supplementation of NSS3.0% and NSS1.5%. Moreover, regulation of the immune response (lysozyme, IgM, ACH50, NO, and MPO), upregulation of IL-10, TGF-β, and IgM, and downregulation of IL-1β, TNF-α, HSP70,and COX-2 were observed following dietary higher NSS levels. After challenge, reduction in A. hydrophila counts was more prominent, especially in NSS3.0% supplemented group. Taken together, the current study encourages the incorporation of such microalgae mix in Nile tilapia's diet for targeting maximum performance, superior fillet quality, and protection against A. hydrophila.

Nutritional immunomodulation of Atlantic salmon response to Renibacterium salmoninarum bacterin

We investigated the immunomodulatory effect of varying levels of dietary ω6/ω3 fatty acids (FA) on Atlantic salmon (Salmo salar) antibacterial response. Two groups were fed either high-18:3ω3 or high-18:2ω6 FA diets for 8 weeks, and a third group was fed for 4 weeks on the high-18:2ω6 diet followed by 4 weeks on the high-18:3ω3 diet and termed "switched-diet". Following the second 4 weeks of feeding (i.e., at 8 weeks), head kidney tissues from all groups were sampled for FA analysis. Fish were then intraperitoneally injected with either a formalin-killed Renibacterium salmoninarum bacterin (5 × 107 cells mL-1) or phosphate-buffered saline (PBS control), and head kidney tissues for gene expression analysis were sampled at 24 h post-injection. FA analysis showed that the head kidney profile reflected the dietary FA, especially for C18 FAs. The qPCR analyses of twenty-three genes showed that both the high-ω6 and high-ω3 groups had significant bacterin-dependent induction of some transcripts involved in lipid metabolism (ch25ha and lipe), pathogen recognition (clec12b and tlr5), and immune effectors (znrf1 and cish). In contrast, these transcripts did not significantly respond to the bacterin in the "switched-diet" group. Concurrently, biomarkers encoding proteins with putative roles in biotic inflammatory response (tnfrsf6b) and dendritic cell maturation (ccl13) were upregulated, and a chemokine receptor (cxcr1) was downregulated with the bacterin injection regardless of the experimental diets. On the other hand, an inflammatory regulator biomarker, bcl3, was only significantly upregulated in the high-ω3 fed group, and a C-type lectin family member (clec3a) was only significantly downregulated in the switched-diet group with the bacterin injection (compared with diet-matched PBS-injected controls). Transcript fold-change (FC: bacterin/PBS) showed that tlr5 was significantly over 2-fold higher in the high-18:2ω6 diet group compared with other diet groups. FC and FA associations highlighted the role of DGLA (20:3ω6; anti-inflammatory) and/or EPA (20:5ω3; anti-inflammatory) vs. ARA (20:4ω6; pro-inflammatory) as representative of the anti-inflammatory/pro-inflammatory balance between eicosanoid precursors. Also, the correlations revealed associations of FA proportions (% total FA) and FA ratios with several eicosanoid and immune receptor biomarkers (e.g., DGLA/ARA significant positive correlation with pgds, 5loxa, 5loxb, tlr5, and cxcr1). In summary, dietary FA profiles and/or regimens modulated the expression of some immune-relevant genes in Atlantic salmon injected with R. salmoninarum bacterin. The modulation of Atlantic salmon responses to bacterial pathogens and their associated antigens using high-ω6/high-ω3 diets warrants further investigation.

Impact of Omega-3 Fatty Acids Nano-Formulation on Growth, Antioxidant Potential, Fillet Quality, Immunity, Autophagy-Related Genes and Aeromonas hydrophila Resistance in Nile Tilapia (Oreochromis niloticus)

In modern aquaculture, enriching Nile tilapia’s diet with omega-3 poly-unsaturated fatty acids (PUFAs) not only plays an important role in its general health but also fortifies its fillet with omega-3-PUFAs. However, the major challenge affecting their delivery is their high instability due to oxidative deterioration. Thus, the prospective incorporation of omega-3-PUFAs into nanocarriers can enhance their stability and bioactivity. In this regard, the effect of reformulated omega-3-NPs was investigated on Nile tilapia’s performance, flesh antioxidant stability, immunity, and disease resistance. Four fish groups supplemented with omega-3-PUFAs-loaded nanoparticles (omega-3 NPs) at levels of 0, 1, 2, and 3 g/kg diet and at the end of feeding trial fish challenged with Aeromonas hydrophila. Fish performance (weight gain and feed conversion) was improved in groups supplemented with omega-3-NPs (2 and 3 g/kg diet). The deposition of omega-3-PUFAs in fish flesh elevated with increasing dietary omega-3-NPs. Simultaneously the oxidative markers (H₂O₂, MDA, and reactive oxygen species) in fish flesh were reduced, especially with higher omega-3-NPs. Post-challenge, downregulation of IL-1β, IL-6, IL-8, TNF-α, and caspase-1 were noticed after dietary supplementation of omega-3-NPs. Moreover, mRNA expression of autophagy-related genes was upregulated while the mTOR gene was downregulated with higher omega-3 NPs levels. Lower expression of A. hydrophila ahyI and ahyR genes were detected with omega-3 NPs supplementation. In conclusion, omega-3-NPs application can fortify tilapia flesh with omega-3-PUFAs and augment its performance, immunity, and disease resistance against Aeromonas hydrophila.

Beneficial effects of re-feeding high α-linolenic acid diets on the muscle quality, cold temperature and disease resistance of tilapia

To investigate the effects of re-feeding high α-linolenic acid (ALA) diets on the muscle quality, cold temperature and disease resistance of the tilapia with nutritional history of soybean oil diets, three experimental diets with linoleic aicd (LA)/ALA ratios at 9 (D1, taking soybean oil as lipid sources), 3 and 1 (D2 and D3, taking soybean and linseed oils as lipid sources) were prepared to re-feed juveniles for 10 weeks, and the growth performance, muscle quality were analyzed. After the re-feeding trial, the fish were fasted for 8 weeks at cold temperature (15°C-20 °C) and then subjected to the Aeromonas hydrophila challenge, and the cold temperature and disease resistance of the fish were evaluated. It was shown that a comparable growth performance was detected among the three dietary groups, while, the high feed efficiency and low viscerosomatic and hepatosomatic index were detected in the D2 and D3 groups compared with the D1 group. In addition, the docosahexaenoic acid (DHA) and n-3 polyunsaturated fatty acid (PUFA) levels of the muscle increased in a parallel pattern with the dietary ALA levels, and the muscular tenderness, adhesiveness, and chewiness were modified substantially in fish fed the diets D2 and D3. After 8-week fasting at cold temperature, the low serum total antioxidant capacity (T-AOC) and malondialdehyde (MDA) levels, and high serum lysozyme (LZM) and C3 levels were observed in the D2 and D3 groups compared with the D1 group. It was also shown that high eicosapentaenoic acid (EPA), DHA, and n-3 PUFA levels were observed in the intestine, liver, and spleen of fish from D2 and D3 groups. Correspondingly, in the fish of the D2 and D3 groups, the mRNA levels of lzm in the liver, intestine, and spleen, and c3 in the intestine and spleen were increased, while the mRNA levels of il-1β, ifn-γ, and tnf-α in the intestine, and ifn-γ, tnf-α in the liver, as well as spleen il-1β, were decreased. Furthermore, the survival at day 15 post-challenge of A. hydrophila in the D2 and D3 groups were higher than those of the D1 group. The results demonstrated that re-feeding high ALA diets were beneficial to the muscle quality, cold temperature and disease resistance in the tilapia, and provide a basis for selecting the dietary lipid sources of tilapia pre-winter feed.

Fatty acid secretion by the white rot fungus, Trametes versicolor

Fungi can acquire and store nutrients through decomposing and converting organic matter into fatty acids. This research demonstrates for the first time that the white-rot fungus Trametes versicolor has the ability to secrete extracellular droplets which can contain a high concentration of long chain fatty acids and unsaturated fatty acids as well as monosaccharides and polysaccharides. The concentration and composition of the fatty acids varied according to the age of the droplet and the feedstock used for growth of the fungi. The results raise the possibility that these droplets could be harvested offering a new approach for the microbial generation of oil from waste.

Modulation of behavioral and neurochemical responses of adult zebrafish by fluoxetine, eicosapentaenoic acid and lipopolysaccharide in the prolonged chronic unpredictable stress model

Long-term recurrent stress is a common cause of neuropsychiatric disorders. Animal models are widely used to study the pathogenesis of stress-related psychiatric disorders. The zebrafish (Danio rerio) is emerging as a powerful tool to study chronic stress and its mechanisms. Here, we developed a prolonged 11-week chronic unpredictable stress (PCUS) model in zebrafish to more fully mimic chronic stress in human populations. We also examined behavioral and neurochemical alterations in zebrafish, and attempted to modulate these states by 3-week treatment with an antidepressant fluoxetine, a neuroprotective omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA), a pro-inflammatory endotoxin lipopolysaccharide (LPS), and their combinations. Overall, PCUS induced severe anxiety and elevated norepinephrine levels, whereas fluoxetine (alone or combined with other agents) corrected most of these behavioral deficits. While EPA and LPS alone had little effects on the zebrafish PCUS-induced anxiety behavior, both fluoxetine (alone or in combination) and EPA restored norepinephrine levels, whereas LPS + EPA increased dopamine levels. As these data support the validity of PCUS as an effective tool to study stress-related pathologies in zebrafish, further research is needed into the ability of various conventional and novel treatments to modulate behavioral and neurochemical biomarkers of chronic stress in this model organism.

EPA's pleiotropic mechanisms of action: a narrative review

Treatment with icosapent ethyl 4 g/day, a highly purified and stable ethyl ester of eicosapentaenoic acid (EPA), demonstrated a significant reduction in atherosclerotic cardiovascular disease (ASCVD) events and death in REDUCE-IT. However, analyses of REDUCE-IT and meta-analyses have suggested that this clinical benefit is greater than can be achieved by triglyceride reduction alone. EPA therefore may have additional pleiotropic effects, including anti-inflammatory and anti-aggregatory mechanisms. EPA competes with arachidonic acid for cyclooxygenase and lipoxygenase, producing anti-inflammatory and anti-aggregatory metabolites rather than the more deleterious metabolites associated with arachidonic acid. Changing the EPA:arachidonic acid ratio may shift metabolic status from pro-inflammatory/pro-aggregatory to anti-inflammatory/anti-aggregatory. EPA also has antioxidant effects and increases synthesis of nitric oxide. Incorporation of EPA into phospholipid bilayers influences membrane structure and may help to prevent cardiac arrhythmias. Clinically, this may translate into improved vascular health, including regression of atherosclerotic plaque. Overall, EPA has a range of pleiotropic effects that contribute to a reduction in ASCVD.

Direct and pleiotropic effects of the Masou Salmon Delta-5 Desaturase transgene in F1 channel catfish (Ictalurus punctatus)

Channel catfish (Ictalurus punctatus) is the primary culture species in the US along with its hybrid made with male blue catfish, I. furcatus. In an effort to improve the nutritional value of channel catfish, the masou salmon Δ5-desaturase like gene (D5D) driven by the common carp beta-actin promoter (βactin) was inserted into channel catfish. The objectives of this study were to determine the effectiveness of βactin-D5D for improving n-3 fatty acid production in F1 transgenic channel catfish, as well as examine pleiotropic effects on growth, proximate analysis, disease resistance, and other performance traits. Transgenic F1 channel catfish showed a 33% increase in the relative proportion of n-3 fatty acids coupled with a 15% decrease in n-6 fatty acids and a 17% decrease in n-9 fatty acids when compared to non-transgenic full-siblings (P < 0.01, P < 0.01, P < 0.01). However, while the relative proportion of n-3 fatty acids was achieved, the total amount of fatty acids in the transgenic fish decreased resulting in a reduction of all fatty acids. Insertion of the βactin-D5D transgene into channel catfish also had large effects on the body composition, and growth of channel catfish. Transgenic channel catfish grew faster, were more disease resistant, had higher protein and moisture percentage, but lower fat percentage than full-sib controls. There were sex effects as performance changes were more dramatic and significant in males. The βactin-D5D transgenic channel catfish were also more uniform in their fatty acid composition, growth and other traits.

Comparative transcriptome analysis reveals ectopic delta-5 and delta-6 desaturases enhance protective gene expression upon Vibrio vulnificus challenge in Tilapia (Oreochromis niloticus)

Background

Tilapia (Oreochromis niloticus) cultures are frequently infected by Vibrio vulnificus, causing major economic losses to production units. Previously, tilapia expressing recombinant delta-5 desaturase and delta-6 desaturase (D56) were found to be resistant to V. vulnificus infection. In this report, we profile the D56-mediated molecular changes underlying this resistance in tilapia. A comparative transcriptome analysis was performed on V. vulnificus-infected wild-type and D56-transgenic tilapia using Illumina’s sequencing-by-synthesis approach. Gene enrichment analysis on differentially expressed unigenes was performed, and the expression patterns were validated by real-time PCR.

Results

Comparative transcriptome analysis was performed on RNA-sequence profiles obtained from wild-type and D56-transgenic tilapia at 0, 6 and 24 h post-infection with V. vulnificaus. GO and KEGG gene enrichment analyses showed that D56 regulates several pathways and genes, including fatty acid (FA) metabolism associated, and inflammatory and immune response. Expression of selected FA metabolism-associated, inflammatory and immune responsive genes was validated by qPCR. The inflammatory and immune responsive genes that are modulated by FA-associated D56 likely contribute to the enhanced resistance against V. vulnificus infection in Tilapia.

Conclusions

Transcriptome profiling and filtering for two-fold change variation showed that 3795 genes were upregulated and 1839 genes were downregulated in D56-transgenic tilapia. These genes were grouped into pathways, such as FA metabolism, FA elongation, FA biosynthesis, biosynthesis of unsaturated FA, FA degradation, inflammation, immune response, and chemokines. FA-associated genes and immune-related genes were modulated by D56 at 6 h and 24 h post infection with V. vulnificus. The expression patterns of FA-related genes, inflammatory genes, antimicrobial peptide genes and immune responsive genes at 0, 3, 6, 12, 24 and 48 h post-infection suggests these genes are involved in the enhanced resistance of D56 transgenic tilapia to V. vulnificus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07521-5.

Zebrafish Models for Pathogenic Vibrios

Vibrio is a large and diverse genus of bacteria, of which most are nonpathogenic species found in the aquatic environment. However, a subset of the Vibrio genus includes several species that are highly pathogenic, either to humans or to aquatic animals. In recent years, Danio rerio, commonly known as the zebrafish, has emerged as a major animal model used for studying nearly every aspect of biology, including infectious diseases. Zebrafish are especially useful because the embryos are transparent, larvae are small and facilitate imaging studies, and numerous transgenic fish strains have been constructed. Zebrafish models for several pathogenic Vibrio species have been described, and indeed a fish model is highly relevant for the study of aquatic bacterial pathogens. Here, we summarize the zebrafish models that have been used to study pathogenic Vibrio species to date.

Impact of expanded FDA indication for icosapent ethyl on enhanced cardiovascular residual risk reduction

Hypertriglyceridemia is associated with increased cardiovascular disease (CVD) risk. The Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial (REDUCE-IT) demonstrated that the purified, stable ethyl ester of eicosapentaenoic acid, icosapent ethyl (IPE), added to statins reduced CVD events by 25% (p < 0.001), leading to an expanded indication in the USA. IPE is now approved as an adjunct to maximally tolerated statins to reduce CVD event risk in adults with triglyceride (TG) levels ≥150 mg/dl and either established CVD or diabetes mellitus plus ≥2 additional CVD risk factors. The new indication allows co-administration of IPE for elevated TG levels with statin treatment, enabling effective residual risk reduction in a broader at-risk population beyond what can be achieved with intensive low-density lipoprotein cholesterol control alone.

Dual expression of transgenic delta-5 and delta-6 desaturase in tilapia alters gut microbiota and enhances resistance to Vibrio vulnificus infection

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), exhibit antibacterial and anti-inflammatory activities. Furthermore, diets rich in n-3 PUFAs are known to improve disease resistance and limit pathogen infection in commercial aquaculture fishes. In this study, we examined the effects of transgenic overexpression of n-3 PUFA biosynthesis genes on the physiological response to bacterial infection in tilapia. We first established tilapia strains with single or dual expression of salmon delta-5 desaturase and/or delta-6 desaturase and then challenged the fish with Vibrio vulnificus infection. Interestingly, our data suggest that n-3 PUFA-mediated alterations in gut microbiota may be important in determining disease outcome via effects on immune response of the host. Both liver- and muscle-specific single and dual expression of delta-5 desaturase and delta-6 desaturase resulted in higher n-3 PUFA content in transgenic fish fed with a LO basal diet. The enrichment of n-3 PUFAs in dual-transgenic fish is likely responsible for their improved survival rate and comparatively reduced expression of inflammation- and immune-associated genes after V. vulnificus infection. Gut microbiome analysis further revealed that dual-transgenic tilapia had high gut microbiota diversity, with low levels of inflammation-associated microbiota (i.e., Prevotellaceae). Thus, our findings indicate that dual expression of transgenic delta-5 and delta-6 desaturase in tilapia enhances disease resistance, an effect that is associated with increased levels of n-3 PUFAs and altered gut microbiota composition.

Liver Transcriptome Profiling Reveals That Dietary DHA and EPA Levels Influence Suites of Genes Involved in Metabolism, Redox Homeostasis, and Immune Function in Atlantic Salmon (Salmo salar)

The optimal dietary requirement of omega-3 long-chain polyunsaturated fatty acids (ω3 LC-PUFA), namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for Atlantic salmon that promotes growth and health warrants careful investigation. We used 44K microarrays to study the influence of increasing levels of dietary DHA + EPA (0, 1.0, and 1.4% of the diet, as formulated) in the presence of high linoleic acid (LA) on Atlantic salmon growth and liver transcriptome. After a 14-week feeding trial, Atlantic salmon fed diet ω3LC0 (i.e. 0% of DHA + EPA) showed significantly lower final weight and weight gain, and higher feed conversion ratio compared with ω3LC1.0 and ω3LC1.4 diet groups. The microarray experiment identified 55 and 77 differentially expressed probes (Rank Products analyses; PFP < 10%) in salmon fed diets ω3LC1.4 and ω3LC1.0 compared with those fed diet ω3LC0, respectively. The comparison between ω3LC1.4 and ω3LC1.0 revealed 134 differentially expressed probes. The microarray results were confirmed by qPCR analyses of 22 microarray-identified transcripts. Several key genes involved in fatty acid metabolism including LC-PUFA synthesis were upregulated in fish fed ω3LC0 compared with both other groups. Hierarchical clustering and linear regression analyses of liver qPCR and fatty acid composition data demonstrated significant correlations. In the current study, 1.0% ω3 LC-PUFA seemed to be the minimum requirement for Atlantic salmon based on growth performance; however, multivariate statistical analyses (PERMANOVA and SIMPER) showed that fish fed ω3LC1.0 and ω3LC1.4 diets had similar hepatic fatty acid profiles but marked differences in the transcript expression of biomarker genes involved in redox homeostasis (mgst1), immune responses (mxb, igmb, irf3, lect2a, srk2, and lyz2), and LC-PUFA synthesis (srebp1, fadsd5, and elovl2). This research has provided new insights into dietary requirement of DHA and EPA and their impact on physiologically important pathways in addition to lipid metabolism in Atlantic salmon.

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.

Effectiveness of omega-3 polyunsaturated fatty acids against microbial pathogens

Microorganisms provide both beneficial and harmful effects to human beings. Beneficial effects come from the symbiotic relationship that exists between humans and microbiota, but then several human illnesses have turned some friendly microbes into opportunistic pathogens, causing several microbial-related diseases. Various efforts have been made to create and utilize antimicrobial agents in the treatment and prevention of these infections, but such efforts have been hampered by the emergence of antimicrobial resistance. Despite extensive studies on drug discovery to alleviate this problem, issues with the toxicity and tolerance of certain compounds and continuous microbial evolution have forced researchers to focus on screening various phytochemical dietary compounds for antimicrobial activity. Linolenic acid and its derivatives (eicosapentaenoic acid and docosahexaenoic acid) are omega-3 fatty acids that have been studied due to their role in human health, being important for the brain, the eye, the cardiovascular system, and general human growth. However, their utilization as antimicrobial agents has not been widely appreciated, perhaps due to a lack of understanding of antimicrobial mechanisms, toxicity, and route of administration. Therefore, this review focuses on the efficacy, mechanism, and toxicity of omega-3 fatty acids as alternative therapeutic agents for treating and preventing diseases associated with pathogenic microorganisms.

Expression of the human TRIM14 and its mutant form (P207L) promotes apoptosis in transgenic loaches

The tripartite-motif (TRIM)14 protein, one of the TRIM family members, was shown to participate in the antiviral and antibacterial defence. Besides, it appears to play an essential role in the processes of oncogenesis. In some types of human tumour cells, TRIM14 has been shown to inhibit apoptosis, while in others-the overexpression of TRIM14 promotes apoptosis. However, whether TRIM14 mediates apoptosis in the normal cells remains unknown. In the present study, we investigated the possible participation of the human TRIM14 gene and its mutant form (620C > T) in the induction of apoptosis in the transgenic larvae loach Misgurnus fossilis L. We observed that the expression of both forms of TRIM14 gene was accompanied by the increase of the frequency of pyknotic nuclei in fish embryos compared to control groups. Accordingly, using the TUNEL assay, the enhanced apoptosis was revealed upon expression of both forms of TRIM14 gene. The transcription of proapoptotic genes (bax, tp53, and casp9) was significantly increased in transgenic loaches expressing human wild-type TRIM14, but remained unchanged upon expression of its mutant form. In addition, the transcription of c-myc was upregulated in transgenic loaches expressing both forms. Thus, it can be assumed that during embryonic development TRIM14 has a proapoptotic effect on the cells via the activation of c-myc, tp53, and bax genes. Apparently, the mutant TRIM14 directs apoptosis via c-myc by p53-independent mechanism.

Combined effect of linolenic acid and tobramycin on Pseudomonas aeruginosa biofilm formation and quorum sensing

Pseudomonas aeruginosa is a ubiquitous Gram negative opportunistic pathogen capable of causing severe nosocomial infections in humans, and tobramycin is currently used to treat P. aeruginosa associated lung infections. Quorum sensing regulates biofilm formation which allows the bacterium to result in fatal infections forcing clinicians to extensively use antibiotics to manage its infections leading to emerging multiple drug resistant strains. As a result, tobramycin is also becoming resistant. Despite extensive studies on drug discovery to alleviate microbial drug resistance, the continued microbial evolution has forced researchers to focus on screening various phytochemicals and dietary compounds for antimicrobial potential. Linolenic acid (LNA) is an essential fatty acid that possesses antimicrobial actions on various microorganisms. It was hypothesized that LNA may affect the formation of biofilm on P. aeruginosa and improve the potency of tobramycin. The present study demonstrated that LNA interfered with cell-to-cell communication and reduced virulence factor production. It further enhanced the potency of tobramycin and synergistically inhibited biofilm formation through P. aeruginosa quorum sensing systems. Therefore, LNA may be considered as a potential agent for adjunctive therapy and its utilization may decrease tobramycin concentration in combined treatment thereby reducing aminoglycoside adverse effects.

Inducible liver-specific overexpression of gankyrin in zebrafish results in spontaneous intrahepatic cholangiocarcinoma and hepatocellular carcinoma formation

Liver cancer is the second leading cause of death worldwide. As such, establishing animal models of the disease is important for both basic and translational studies that move toward developing new therapies. Gankyrin is a critical oncoprotein in the genetic control of liver pathology. In order to evaluate the oncogenic role of gankyrin without cancer cell inoculation and drug treatment, we overexpressed gankyrin under the control of the fabp10a promoter. A Tet-Off system was used to drive expression in hepatocytes. At seven to twelve months of age, gankyrin transgenic fish spontaneously incurred persistent hepatocyte damage, steatosis, cholestasis, cholangitis, fibrosis and hepatic tumors. The tumors were both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). ICC is the second most frequent primary liver cancer in human patients and the first to develop in this tumor model. We further investigated the role of complement C3, a central molecule of the complement system, and found the expression levels of both in mRNA and protein are decreased during tumorigenesis. Together, these findings suggest that gankyrin can promote malignant transformation of liver cells in the context of persistent liver injury. This transformation may be related to compensatory proliferation and the inflammatory microenvironment. The observed decrease in complement C3 may allow transforming cells to escape coordinated induction of the immune response. Herein, we demonstrate an excellent zebrafish model for liver cancers that will be useful for studying the molecular mechanisms of tumorgenesis.

Transcriptome analysis of the effect of polyunsaturated fatty acids against Vibrio vulnificus infection in Oreochromis niloticus

Vibrio vulnificus infection causes severe economic losses in Oreochromis niloticus aquaculture by inducing pro-inflammatory cytokines, that lead to inflammation and mortality. Omega-3 fatty acids, such as Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA), have been reported for their anti-inflammatory and antibacterial abilities in murine and zebrafish models. However, the anti-inflammatory and antibacterial functions of DHA and EPA in commercial aquaculture organisms such as Oreochromis niloticus remain unknown. The present study demonstrates antibacterial function and transcriptional modulation of inflammation-associated genes by DHA and EPA in Vibrio vulnificus infection in Oreochromis niloticus fish models. The administration of EPA or DHA improved the Oreochromis niloticus survival rate against Vibrio vulnificus infection. The induction of proinflammatory cytokines, Interleukin (IL)-1β, IL-6, Tumor necrosis factor (TNF)-α, and Toll-like receptor (TLR)-2 by Vibrio vulnificus was suppressed in fish that were administered DHA. Bacterial membrane disruption and the killing of Vibrio vulnificus by EPA and DHA was observed using SEM, TEM, and cytoplasm leakage studies. In silico analysis of the transcription profile in Ingenuity Pathway Analysis software showed that DHA may enhance anti-Vibrio vulnificus activity in Oreochromis niloticus via the activation of peroxisome proliferator-activated receptor α (PPARα) to inhibit nuclear factor kappa B and suppress hepatocyte nuclear factor 4 α (HNF4α). In summary, the results of the present study demonstrated that DHA and EPA reduce the severity of Vibrio vulnificus infection and increase the survival rate of Oreochromis niloticus.