In vitro effects of the neuroactive substances serotonin and γ-aminobutyric acid on leucocytes from sticklebacks (Gasterosteus aculeatus). Issue 87 (April 2019)

• Record Type: Journal Article
• Authors: Kutyrev, Ivan A.; Franke, Frederik; Kurtz, Joachim; Scharsack, Jörn P.
• Is Part Of: Fish & shellfish immunology. Issue 87(2019)
• Page Start: 286
• Page End: 296
• Publication Date: 2019-04
• Subjects: Parasite immunomodulation -- Serotonin -- γ-aminobutyric acid -- Cestodes -- In vitro leucocyte responses -- Gasterosteus aculeatus -- Schistocephalus solidus; 5-HT 5-hydroxytryptamine -- Ctrl CM culture medium alone -- Ctrl HCl control concentration of HCl solvent -- GABA γ-aminobutyric acid -- G/L granulocyte-to-lymphocyte ratio -- HKL head kidney leucocytes -- LPS Salmonella typhosa lipopolysaccharides -- PBS phosphate-buffered saline -- RLU relative luminescence units -- ROS reactive oxygen species -- SS Schistocephalus solidus antigens; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2019.01.022
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: The majority of parasites have evolved strategies to evade the immune responses of their hosts. Neuroactive substances produced by cestodes are possible candidate molecules for regulating host immune responses. The neurons of helminths can synthesize a wide range of molecules that are identical to the ones functioning in their host organisms, and host lymphocytes have receptors for these neuroactive substances. We hypothesized that in teleost fish, antihelminthic immune responses are regulated via 5-hydroxytryptamine (5-HT, or serotonin) and γ-aminobutyric acid (GABA). In the present study, we investigated the in vitro influence of serotonin, GABA and Schistocephalus solidus (helminth) antigens on basic characteristics of the three-spined stickleback Schistocephalus solidus cellular immune response. Head kidney leucocytes (HKLs) were analysed by flow cytometry for cell viability and the frequency of leucocyte subsets (the granulocyte-to-lymphocyte ratio) and by a chemiluminescence assay for the production of reactive oxygen species (ROS). In short-term (2-h) HKL cultures, 5-HT did not change the total numbers of live HKLs, but the production of ROS decreased significantly with all 5-HT concentrations. In long-term (96-h) cultures, high 5-HT concentrations induced a decrease in leucocyte viability. This coincided with elevated ROS production in cultures with all 5-HT concentrations. In short-term (2-h) HKL cultures, GABA did not change the total numbers of live HKLs, but the production of ROS decreased significantly with high (100 nmol L −1 ) GABA concentrations. In long-term (96-h) cultures, high and medium concentrations of GABA (100 nmol L −1 and 10 nmol L −1 ) elevated the numbers of live HKLs compared to controls. The granulocyte-to-lymphocyte ratios generally increased upon exposure to GABA at all concentrations. All concentrations of GABA alone elevated the ROS production of HKLs compared to controls. In the present work, we showed that the neuroactive substances serotonin and GABA regulate the teleost immune system. Our study supports the hypothesis that these substances might be immunomodulators in tapeworm–fish parasite-host interactions. Graphical abstract: Image 1 Highlights: 5-HT decreased leucocytes viability in long-term cultures. GABA increased leucocytes viability in long-term cultures. GABA increased granulocyte to leucocyte ratios in long-term cultures. 5-HT and GABA decreased ROS production in short-term and increased in long-term cultures. 5-HT and GABA might be immunomodulators in Cestode – fish interactions.