Persistent Oxytetracycline Exposure Induces an Inflammatory Process That Improves Regenerative Capacity in Zebrafish Larvae

BACKGROUND: The excessive use of antibiotics in aquaculture can adversely affect not only the environment, but also fish themselves. In this regard, there is evidence that some antibiotics can activate the immune system and reduce their effectiveness. None of those studies consider in detail the adverse inflammatory effect that the antibiotic remaining in the water may cause to the fish. In this work, we use the zebrafish to analyze quantitatively the effects of persistent exposure to oxytetracycline, the most common antibiotic used in fish farming. METHODOLOGY: We developed a quantitative assay in which we exposed zebrafish larvae to oxytetracycline for a period of 24 to 96 hrs. In order to determinate if the exposure causes any inflammation reaction, we evaluated neutrophils infiltration and quantified their total number analyzing the Tg(mpx:GFP)(i114) transgenic line by fluorescence stereoscope, microscope and flow cytometry respectively. On the other hand, we characterized the process at a molecular level by analyzing several immune markers (il-1β, il-10, lysC, mpx, cyp1a) at different time points by qPCR. Finally, we evaluated the influence of the inflammation triggered by oxytetracycline on the regeneration capacity in the lateral line. CONCLUSIONS: Our results suggest that after 48 hours of exposure, the oxytetracycline triggered a widespread inflammation process that persisted until 96 hours of exposure. Interestingly, larvae that developed an inflammation process showed an improved regeneration capacity in the mechanosensory system lateral line

Phylogeny of interleukins: growth factors produced by leucocytes of the cyprinid fish, Cyprinus carpio L.

Supernatants of phytohaemagglutinin (PHA)-activated pronephric leucocytes from carp (Cyprinus carpio L.) contain a lymphocyte growth factor which can induce a proliferative response of purified lymphoblasts but not freshly isolated leucocytes. The growth-promoting activity can be reduced by absorbing the supernatant with mitogen-activated blasts. In addition, increased incorporation of tritiated thymidine into PHA-activated blast cells is also induced by supernatants from two-way mixed leucocyte cultures. The data show that even at the evolutionary level of teleost fish, amplifying/regulatory leucocyte products exist. It is suggested that these factors play as important a role in the regulation of the immune response in fish as they do in mammals