| Abstract | The presence of potentially immunotoxic chemicals in surface waters and the adverse effects associated with exposures to such substances is of great concern. However, robust models have not been developed to screen chemicals for immunotoxicity before they are discharged into the environment. The fathead minnow (FHM, Pimephales promelas) has been identified as a potential immunotoxicology model. The effects of dexamethasone, (a known immunosuppressive agent) on pathogen resistance, and the resting and pathogen-stimulated immune system of FHMs were investigated in this study. The fish were divided into 3 groups (Solvent control, low-dose, and high-dose) with a portion injected with Hank's balanced salt solution (Sham-injected) and others injected with Y. ruckeri (Pathogen-injected). The results showed that following pathogen infection, FHMs exposed to dexamethasone had less survival relative to the solvent control. Upon treatment with dexamethasone, blood glucose level was significantly increased in the low-dose relative to the high-dose and solvent control pathogen-injected male FHMs. There were no significant alterations in the expression of il-1ß, il-10, tnf-a, and elas2 in in FHMs response to dexamethasone. There were significant alterations in SSI, hematocrit, and the expression of il-11, cox2, 16s, c3 and c9 in response to dexamethasone and SSI, cox2, c3 and c9 expression were altered in response to dexamethasone and pathogen interaction. The significant downregulation of c3 and c9 in the high-dose sham-injected male fish is indicative of the immunosuppressive effects of dexamethasone. There were significant differences in SSI, hematocrit, and hepatic immune-related gene expression (except elas2) between the sham-injected and pathogen-injected FHMs. The pathogen-injected FHM experienced a significant increase in SSI, significant decrease in hematocrit and significant upregulation in the expression of immune related genes (il-1ß, il-10, il-11, cox2, tnf-a, 16s, c3 and c9) except for elas2 relative to the sham-injected FHMs. The results from this study demonstrated that that the FHMs are an ideal model for immunotoxicology studies, however, there is a need to study the effects of dexamethasone at different time points for an extended period and its impact on immune related gene expression in other tissues. |
