Injection of Resperpine into Zebrafish, Prevents Fish to Fish Communication of Radiation-Induced Bystander Signals: Confirmation in vivo of a Role for Serotonin in the Mechanism

Abstract

ᮀ Serotonin (5-HT) has been implicated as a potential modulator of the bystander effect in cell cultures. To assess the relevance of serotonin in vivo experiments were done with the zebrafish (Danio rerio). This species, when irradiated, transmits bystander signals to non-irradiated fish. The animals were injected with reserpine, an inhibitor of serotonin at a dose of 80mg/kg of body mass. The results show that reserpine treated fish had only 27% of the serotonin in non-treated fish. Skin tissue samples were collected from the fish and assayed for bystander signal production using a reporter bioassay. Reserpine prevented the production and communication of signals between fish. Intracellular calcium flux, identified as a bystander response in the reporter cells confirmed this. Medium harvested from tissues of X-rayed fish and their bystanders, showed an oscillating pattern of calcium flux. Samples from X-rayed fish pretreated with reserpine produced a chaotic pattern of random fluctuations in the reporter cells, while their bystander fish led to increased calcium, but no oscillations. These results suggest that 5-HT is involved in bystander signalling in zebrafish, and by decreasing the amount of available 5-HT the bystander effect can be blocked.

Short and long term bystander effect induction by fathead minnows (Pimephales promelas, Rafinesque, 1820) injected with environmentally relevant whole body doses of 226Ra

“…Instead it is more likely these effects were the result of chemical (Mothersill et al, 2012(Mothersill et al, , 2009(Mothersill et al, , 2007(Mothersill et al, , 2006Saroya et al, 2010;Smith et al, 2013Smith et al, , 2011 and/or physical (Mothersill et al, 2012) signals emitted from the irradiated fish.…”

“…In doing so this study adds alpha particles to X-rays (Mothersill et al, 2012(Mothersill et al, , 2009(Mothersill et al, , 2007(Mothersill et al, , 2006Saroya et al, 2010;Smith et al, 2013Smith et al, , 2011 and gamma Table 2 Results of 0.5 Gy X-ray positive controls of the HPV-G reporter cell assay carried out at each post-injection time interval. * indicates clonogenic survival significantly different from untreated fish.…”

“…The methods for inducing a bystander effect, the collection of tissue samples and the Human Papilloma Virus strain G transfected human keratinocytes (HPV-G) reporter cell clonogenic assay, for determining the induction of a pro-or anti-apoptotic effect, in fish of this size, have all been previously described (Mothersill et al, 2007(Mothersill et al, , 2009(Mothersill et al, , 2012Saroya et al, 2010;Smith et al, 2011;Wang et al, 2011). Briefly, groups of 4 injected fish were placed in one side of a mesh partitioned container.…”

“…A positive control group of fish was included in each assessment. These fish were given a single 0.5 Gy X-ray dose since this has already been shown to induce a bystander effect in trout (Mothersill et al, , 2006, zebrafish (Mothersill et al, 2012(Mothersill et al, , 2007Saroya et al, 2010) and medaka (Mothersill et al, 2009;Smith et al, 2011). Sham X-ray treatments were also included to control for the handling and confinement stress of the X-ray irradiation.…”

“…There is now an increasing amount of data to show that fish, when irradiated with low doses of radiation, are able to induce a bystander effect in non-irradiated fish. Predominantly this research has been carried out using 0.5 Gy X-ray irradiation (Mothersill et al, 2012(Mothersill et al, , 2009(Mothersill et al, , 2007(Mothersill et al, , 2006Saroya et al, 2010;Smith et al, 2013Smith et al, , 2011. X-rays have the advantage of not making the irradiated fish radioactive.…”