Recurrent oxidant treatment induces dysregulation in the brain transcriptome of Atlantic salmon (Salmo salar) smolts

publishedVersio

Multiomics Provide Insights into the Key Molecules and Pathways Involved in the Physiological Adaptation of Atlantic Salmon (Salmo salar) to Chemotherapeutic-Induced Oxidative Stress

Although chemotherapeutics are used to treat infections in farmed fish, knowledge on how they alter host physiology is limited. Here, we elucidated the physiological consequences of repeated exposure to the potent oxidative chemotherapeutic peracetic acid (PAA) in Atlantic salmon (Salmo salar) smolts. Fish were exposed to the oxidant for 15 (short exposure) or 30 (long exposure) minutes every 15 days over 45 days. Unexposed fish served as the control. Thereafter, the ability of the remaining fish to handle a secondary stressor was investigated. Periodic chemotherapeutic exposure did not affect production performance, though survival was lower in the PAA-treated groups than in the control. Increased ventilation, erratic swimming, and a loss of balance were common behavioural manifestations during the oxidant exposure. The plasma reactive oxygen species levels increased in the PAA-treated groups, particularly after the third exposure, suggesting an alteration in the systemic oxidative stress status. Plasma indicators for internal organ health were affected to a certain degree, with the changes mainly observed after the second and third exposures. Metabolomics disclosed that the oxidant altered several circulating metabolites. Inosine and guanosine were the two metabolites significantly affected by the oxidative stressor, regardless of exposure time. A microarray analysis revealed that the gills and liver were more responsive to the oxidant than the skin, with the gills being the most sensitive. Moreover, the magnitude of the transcriptomic modifications depended on the exposure duration. A functional analysis showed that genes involved in immunity and ribosomal functions were significantly affected in the gills. In contrast, genes crucial for the oxidation-reduction process were mainly targeted in the liver. Skin mucus proteomics uncovered that the changes in the mucosal proteome were dependent on exposure duration and that the oxidant interfered with ribosome-related processes. Mucosal mapping revealed gill mucous cell hypertrophy after the second and third exposures, although the skin morphological parameters remained unaltered. Lastly, repeated oxidant exposures did not impede the ability of the fish to mount a response to a secondary stressor. This study provides insights into how a chemical oxidative stressor alters salmon physiology at both the systemic and mucosal levels. This knowledge will be pivotal in developing an evidence-driven approach to the use of oxidative therapeutics in fish, with some of the molecules and pathways identified as potential biomarkers and targets for assessing the physiological cost of these treatments.publishedVersio

Regulation of the molecular repertoires of oxidative stress response in the gills and olfactory organ of Atlantic salmon following infection and treatment of the parasite Neoparameoba perurans

publishedVersio

Mucosal immune and stress responses of Neoparamoeba perurans-infected Atlantic salmon (Salmo salar) treated with peracetic acid shed light on the host-parasite-oxidant interactions

Treatment development for parasitic infestation is often limited to disease resolution as an endpoint response, and physiological and immunological consequences are not thoroughly considered. Here, we report the impact of exposing Atlantic salmon affected with amoebic gill disease (AGD) to peracetic acid (PAA), an oxidative chemotherapeutic. AGD-affected fish were treated with PAA either by exposing them to 5 ppm for 30 min or 10 ppm for 15 min. Unexposed fish from both infected and uninfected groups were also included. Samples for molecular, biochemical, and histological evaluations were collected at 24 h, 2 weeks, and 4 weeks post-treatment. Behavioral changes were observed during PAA exposure, and post-treatment mortality was higher in the infected and PAA treated groups, especially in 10 ppm for 15 min. Plasma indicators showed that liver health was affected by AGD, though PAA treatment did not exacerbate the infection-related changes. Transcriptome profiling in the gills showed significant changes, triggered by AGD and PAA treatments, and the effects of PAA were more notable 24 h after treatment. Genes related to immune pathways of B- and T- cells and protein synthesis and metabolism were downregulated, where the magnitude was more remarkable in 10 ppm for 15 min group. Even though treatment did not fully resolve the pathologies associated with AGD, 5 ppm for 30 min group showed lower parasite load at 4 weeks post-treatment. Mucous cell parameters (i.e., size and density) increased within 24 h post-treatment and were significantly higher at termination, especially in AGD-affected fish, with some treatment effects influenced by the dose of PAA. Infection and treatments resulted in oxidative stress—in the early phase in the gill mucosa, while systemic reactive oxygen species (ROS) dysregulation was evident at the later stage. Infected fish responded to elevated circulating ROS by increasing antioxidant production. Exposing the fish to a crowding stress revealed the interference in the post-stress responses. Lower cortisol response was displayed by AGD-affected groups. Collectively, the study established that PAA, within the evaluated treatment protocols, could not provide a convincing treatment resolution and, thus, requires further optimization. Nonetheless, PAA treatment altered the mucosal immune and stress responses of AGD-affected Atlantic salmon, shedding light on the host-parasite-treatment interactions.publishedVersio

Ultrasound as potential inhibitor of salmon louse infestation - a small-scale study

submittedVersio

Probiotic Carnobacterium divergens increase growth parameters and disease resistance in farmed Atlantic cod (Gadus morhua) larvae without influencing the microbiota

Aquaculture represents the fastest growing food sector and the second largest export commodity in Norway. Disease in aquaculture causes mortality and huge losses in farmed fish. Probiotic treatment of farmed fish, i.e. feeding of fish with live, beneficial microorganisms, may represent one part of a sustainable solution to these problems. Some carnobacteria of fish origin have shown promising results as probiotics for fish. In this study, two Carnobacterium divergens strains were fed to Atlantic cod (Gadus morhua) larvae through intermittent feeding with Artemia franciscana containing the bacterial strains. Cod larvae fed with the carnobacteria showed a significantly higher growth and survival during the larval rearing stage compared to the larvae fed A. franciscana with no carnobacteria (control treatment). Following the probiotic feeding period, the cod larvae were challenged with a pathogenic bacterium, Vibrio anguillarum. Cod larvae from probiotic treatment showed significantly better disease resistance compared to the control. Microbiota analysis by 16S rRNA amplicon sequencing verified that enrichment of carnobacteria in the A. franciscana feed. Analysis of the whole larvae detected only minor relative levels of carnobacteria in the probiotic treated larvae, which was non-significant compared to the control larvae (p = 0.062). The probiotic treatment had no significant impact on the overall microbiota diversity or composition in the larvae during the probiotic feeding period or after the disease challenge. Despite this, significantly improved growth and survival during larval rearing and post-pathogen challenge suggest probiotic effects of C. divergens mixture on cod larval fish performance and welfare. Studies examining the mode of action should be carried out to get more insight to lead to the commercial application of C. divergens in Atlantic cod larviculture.publishedVersio

Kvalitetsforskjeller på fersk og tint filet fra torsk: Objektive målinger

Ferske og tinte torskefileter er sammenlignet med bruk av sensorisk panel og vurdering av filetindeks, samt måling av vanninnhold, protein, aske, totalt flyktig nitrogen (TVN), trimetylamin (TMA), trimetylaminoksid (TMAO), totalkim og sulfidproduserende bakterier. Det er funnet små forskjeller mellom fersk torskefilet lagret en uke på is og nytint torskefilet/torskefilet lagret på is 2 dager etter tining. Funnene i denne rapporten dokumenterer ikke til fulle forskjeller eller likheter på kategoriene ”fersk” eller ”tint”. Dette skyldes at både fersk og tint fisk endrer kvalitet og egenskaper betydelig under lagringen etter slakting/tining, slik at alderen på råstoffet av stor betydning. Resultatene i dette arbeidet kan benyttes som veiledende til hvilke kvalitetsutviklinger og egenskaper man kan forvente dersom man har ferskt og tint råstoff av god kvalitet tilgjengelig for presentasjon i kjøledisker.Rapport/Report 31/2011 English summaryKvalitetsforskjeller på fersk og tint filet fra torsk: Objektive målingerpublishedVersio

RSW-, CSW- og iskjøling av råstoff (torsk), konsekvenser for filetkvaliteten - forsøk 2011

I forsøket ble torsk bløgget, utblødd i vann, sløyd og vasket på en identisk måte og deretter kjølt som hel fisk i 1, 2 og 3 døgn i henholdsvis RSW, CSW eller iset i kasser. Målet var å undersøke om disse kjølemetodene for råstoffet resulterte i ulik kvalitet på filetene. Filetkvaliteten ble vurdert sensorisk, muskelfargen ble målt instrumentelt, vann og salt ble analysert. Etter lagring av fileter frem til dag 10 p.m. ble det utført analyser av mikroflora og TVN. Hovedkonklusjonen er at tørr ising av råstoff i kasser gav bedre kvalitet på filetene enn tilsvarende lang kjøling av råstoff i sjøvann (RSW og CSW). Særlig tydelig var dette i fileter som ble lagret kjølt etter skjæring, frem til 10 døgn etter at fisken ble slaktet. At tradisjonell tørr ising av torsk i kasser eller kar gir bedre filetkvalitet enn kjøling av råstoffet i vann er et resultat som bør tas med i vurderingen av hvordan fisk bør kjøles ombord på fiskefartøy, for å oppnå best mulig kvalitet på råstoffet.RSW-, CSW- og iskjøling av råstoff (torsk), konsekvenser for filetkvaliteten - forsøk 2011publishedVersio

Multiomics Provide Insights into the Key Molecules and Pathways Involved in the Physiological Adaptation of Atlantic Salmon (Salmo salar) to Chemotherapeutic-Induced Oxidative Stress

Although chemotherapeutics are used to treat infections in farmed fish, knowledge on how they alter host physiology is limited. Here, we elucidated the physiological consequences of repeated exposure to the potent oxidative chemotherapeutic peracetic acid (PAA) in Atlantic salmon (Salmo salar) smolts. Fish were exposed to the oxidant for 15 (short exposure) or 30 (long exposure) minutes every 15 days over 45 days. Unexposed fish served as the control. Thereafter, the ability of the remaining fish to handle a secondary stressor was investigated. Periodic chemotherapeutic exposure did not affect production performance, though survival was lower in the PAA-treated groups than in the control. Increased ventilation, erratic swimming, and a loss of balance were common behavioural manifestations during the oxidant exposure. The plasma reactive oxygen species levels increased in the PAA-treated groups, particularly after the third exposure, suggesting an alteration in the systemic oxidative stress status. Plasma indicators for internal organ health were affected to a certain degree, with the changes mainly observed after the second and third exposures. Metabolomics disclosed that the oxidant altered several circulating metabolites. Inosine and guanosine were the two metabolites significantly affected by the oxidative stressor, regardless of exposure time. A microarray analysis revealed that the gills and liver were more responsive to the oxidant than the skin, with the gills being the most sensitive. Moreover, the magnitude of the transcriptomic modifications depended on the exposure duration. A functional analysis showed that genes involved in immunity and ribosomal functions were significantly affected in the gills. In contrast, genes crucial for the oxidation-reduction process were mainly targeted in the liver. Skin mucus proteomics uncovered that the changes in the mucosal proteome were dependent on exposure duration and that the oxidant interfered with ribosome-related processes. Mucosal mapping revealed gill mucous cell hypertrophy after the second and third exposures, although the skin morphological parameters remained unaltered. Lastly, repeated oxidant exposures did not impede the ability of the fish to mount a response to a secondary stressor. This study provides insights into how a chemical oxidative stressor alters salmon physiology at both the systemic and mucosal levels. This knowledge will be pivotal in developing an evidence-driven approach to the use of oxidative therapeutics in fish, with some of the molecules and pathways identified as potential biomarkers and targets for assessing the physiological cost of these treatments

Probiotic Carnobacterium divergens increase growth parameters and disease resistance in farmed Atlantic cod (Gadus morhua) larvae without influencing the microbiota

Aquaculture represents the fastest growing food sector and the second largest export commodity in Norway. Disease in aquaculture causes mortality and huge losses in farmed fish. Probiotic treatment of farmed fish, i.e. feeding of fish with live, beneficial microorganisms, may represent one part of a sustainable solution to these problems. Some carnobacteria of fish origin have shown promising results as probiotics for fish. In this study, two Carnobacterium divergens strains were fed to Atlantic cod (Gadus morhua) larvae through intermittent feeding with Artemia franciscana containing the bacterial strains. Cod larvae fed with the carnobacteria showed a significantly higher growth and survival during the larval rearing stage compared to the larvae fed A. franciscana with no carnobacteria (control treatment). Following the probiotic feeding period, the cod larvae were challenged with a pathogenic bacterium, Vibrio anguillarum. Cod larvae from probiotic treatment showed significantly better disease resistance compared to the control. Microbiota analysis by 16S rRNA amplicon sequencing verified that enrichment of carnobacteria in the A. franciscana feed. Analysis of the whole larvae detected only minor relative levels of carnobacteria in the probiotic treated larvae, which was non-significant compared to the control larvae (p = 0.062). The probiotic treatment had no significant impact on the overall microbiota diversity or composition in the larvae during the probiotic feeding period or after the disease challenge. Despite this, significantly improved growth and survival during larval rearing and post-pathogen challenge suggest probiotic effects of C. divergens mixture on cod larval fish performance and welfare. Studies examining the mode of action should be carried out to get more insight to lead to the commercial application of C. divergens in Atlantic cod larviculture