Alleviating effects of essential oil from Artemisia vulgaris on enteritis in zebrafish via modulating oxidative stress and inflammatory response

Artemisia vulgaris (A. vulgaris) is a traditional Chinese medicine widely distributed in China and contains many bioactive compounds with pharmacological effects. However, the anti-inflammatory effects and mechanism of essential oil from A. vulgaris on enteritis in fish are still unclear. In this study, in order to elucidate the underlying mechanism of essential oil from A. vulgaris on zebrafish enteritis, zebrafish were used for establishing animal models to observe the histopathological changes of intestines, determine the activities of immune-related enzymes and oxidative stress indicators, and the mRNA expression of genes in MyD88/TRAF6/NF-KB signaling pathways. The results showed that different doses of A. vulgaris essential oil could effectively alleviate zebrafish enteritis in a dose- and time-dependent manner by improving the intestinal histopathological damage, decreasing the intestinal oxidative stress, repairing the intestinal immune ability, changing the expression levels of IL-1β, IL-10 and genes in MyD88/TRAF6/NF-κB pathway. In addition, co-treatment with oxazolone and MyD88 inhibitor could alleviate the morphological damage, the induction of oxidative stress, and the levels of immune-related enzymes and the mRNA expression of genes in MyD88/TRAF6/NF-κB signaling pathway. Moreover, essential oil from A. vulgaris had more significantly therapeutic effects on enteritis of male zebrafish than that of female zebrafish. This result will clarify the therapeutic effect and anti-inflammatory mechanism of essential oil from A. vulgaris on zebrafish enteritis, and provide a theoretical basis for further research on the rationality of A. vulgaris to replace feed antibiotics.

A non-lethal method for detection of Bonamia ostreae in flat oyster (Ostrea edulis) using environmental DNA

Surveillance and diagnosis of parasitic Bonamia ostreae infections in flat oysters (Ostrea edulis) are prerequisites for protection and management of wild populations. In addition, reliable and non-lethal detection methods are required for selection of healthy brood oysters in aquaculture productions. Here we present a non-lethal diagnostic technique based on environmental DNA (eDNA) from water samples and demonstrate applications in laboratory trials. Forty oysters originating from Limfjorden, Denmark were kept in 30 ppt sea water in individual tanks. Water was sampled 6 days later, after which all oysters were euthanized and examined for infection, applying PCR. Four oysters (10%) were found to be infected with B. ostreae in gill and mantle tissue. eDNA purified from the water surrounding these oysters contained parasite DNA. A subsequent sampling from the field encompassed 20 oysters and 15 water samples from 5 different locations. Only one oyster turned out positive and all water samples proved negative for B. ostreae eDNA. With this new method B. ostreae may be detected by only sampling water from the environment of isolated oysters or isolated oyster populations. This non-lethal diagnostic eDNA method could have potential for future surveys and oyster breeding programs aiming at producing disease-free oysters.

Differential immune gene response in gills, skin, and spleen of rainbow trout Oncorhynchus mykiss infected by Ichthyophthirius multifiliis

Infection of rainbow trout with the parasitic ciliate Ichthyopthirius multifiliis induces differential responses in gills, skin and spleen. A controlled experimental infection was performed and expression of immune-relevant genes in skin, gills, and spleen were recorded by qPCR at day 1 and 8 after parasite exposure. Infection induced a marked reaction involving regulation of innate and adaptive immune genes in rainbow trout at day 8 post-infection. The expression level of a total of 22 out of 24 investigated genes was significantly higher in gills compared to skin reflecting the more sensitive and delicate structure of gills. Especially pro-inflammatory cytokines IL-6, IL-17 C1, regulatory cytokines IL-4/13A, IL-10, TGFβ, complement factor C5, chemokines CK10, CK12, acute phase proteins (precerebellin, hepcidin) and immunoglobulins (IgM, IgT) displayed differential expression levels. The spleen, a central immune organ with no trace of the parasite, showed elevated expression of IgM, IgT, complement factor C5 and chemokine CK10 (compared to skin and gills directly exposed to the parasite), indicating an interaction between the infected surface sites and central immune organs. This communication could be mediated by chemokines CK10 and CK12 and cytokine IL-4/13A and may at least partly explain the establishment of a systemic response in rainbow trout against the parasite.

Cannabidiol effects on behaviour and immune gene expression in zebrafish (Danio rerio)

Various preparations and extracts of the plant Cannabis sativa (family cannabaceae) are used as herbal medicinal drugs against a series of disorders but the plant contains a wide series of pharmacologically active components which may confound evaluation of drug effects. In order to differentiate specific effects of the individual constituents on specific functions in the organism we advocate for controlled studies on specified constituents and their impact on the vertebrate organism. One of the dominating Cannabis constituents, delta(9)-tetrahydrocannabinol (THC), has previously been studied in depth whereas information on another main ingredient cannabidiol (CBD) is limited. We have performed a controlled study on CBD and its effect using an experimental zebrafish model. CDB treatment of zebrafish for 30 min affected mobility of the fish by decreasing swimming speed and swimming distance. In addition, out of 23 immune related genes studied it was shown that expression of two genes il1b and il17a/f2 were up-regulated and four genes, tgfba, ighm, cd4-1, and s100a10b were significantly down-regulated following CBD treatment. The study indicated that CBD affects motility and immunity of the vertebrate host.

Effect of ES products from Anisakis (Nematoda: Anisakidae) on experimentally induced colitis in adult zebrafish

Inflammatory bowel disease (IBD) in developed countries is linked with elevated hygienic standards. One of the several factors involved in this question may be reduced exposure to the immunomodulatory effects of parasitic helminths. Several investigations on treatment of mice and humans with helminth-derived substances have supported this notion, but underlying mechanisms remain unclear. This study therefore dissects to what extent a series of immune-related genes are modulated in zebrafish with experimentally induced colitis following exposure to excretory-secretory (ES) products isolated from larval Anisakis, a widely distributed fish nematode. Adult zebrafish intrarectally exposed to the colitis-inducing agent TNBS developed severe colitis leading to 80% severe morbidity, but if co-injected (ip) with Anisakis ES products, the morbidity rate was 50% at the end of the experiment (48 hours post-exposure). Gene expression studies of TNBS-treated zebrafish showed clear upregulation of a range of genes encoding inflammatory cytokines and effector molecules and some induction of genes related to the adaptive response. A distinct innate-driven immune response was seen in both TNBS and TNBS + ES groups, but expression values were significantly depressed for several important pro-inflammatory genes in the TNBS + ES group, indicating protective mechanisms of Anisakis ES compounds on intestinal immunopathology in zebrafish.

Zebrafish (Danio rerio) as a model to visualize infection dynamics of Vibrio anguillarum following intraperitoneal injection and bath exposure

Vaccine development is important for sustainable fish farming and novel vaccines need to be efficacy tested before release to the market. Challenge of fish with the pathogen towards which the vaccine has been produced can be conducted either by external exposure though bathing or cohabitation, or by bypassing the mucosa through injection. The latter approach is often preferred since it is easier to control than the former. However, injection is not a very natural route of infection, and the bypass of the mucosa may result in a different efficacy profile of experimental fish compared to farmed fish, for which the vaccines are targeted. The zebrafish is by now a well established practical vertebrate model species due in part to its size and ease of maintenance and genetic manipulation. Here we use zebrafish as a model to visualize and compare the development of infection of Vibrio anguillarum on and in the fish following injection or bathing. Injection of 10³ bacteria per fish resulted in approximately 50% mortality by day 4 post-injection. Similar mortality levels were reached in the other group by bathing in 1.25 × 10⁹ bacteria for 1 min. The spreading of bacteria was followed for the first 24 h after injection/bathing by immunohistochemistry and optical projection tomography. The tissues and organs where bacteria were detected differed significantly as a result of time as well as treatment. In the bath group, bacteria were initially found on external surfaces including gut. After 24 h V. anguillarum still persisted in gut but had now also spread to the blood. In the injection group bacteria were found in the blood throughout all sampling times, as well as in the hypodermis and body cavity at most sampling times.

Immunomodulatory effects of excretory/secretory compounds from Contracaecum osculatum larvae in a zebrafish inflammation model

Excretory/secretory (ES) compounds isolated from third-stage larvae of the anisakid nematode Contracaecum osculatum parasitizing liver of Baltic cod were investigated for effects on immune gene expression in a zebrafish LPS-induced inflammation model. ES products containing a series of proteins, of which some had enzymatic activity, were injected solely or with LPS. ES proteins alone induced up-regulation of a number of immune-related genes, but generally to a lower degree compared to LPS. When co-injected with LPS, the worm products exacerbated merely expression of five genes affecting Th1, Th2, Th17 and innate responses compared to the LPS-injected group. However, the level of overexpression decreased in an inverse dose-dependent manner. The immune regulating action of C. osculatum ES products is interpreted as an important evolutionary ability of larval parasites in the transport host which makes it less susceptible to host immune responses whereby the probability of reaching the final host is increased.