Effects of arsenic on zebrafish innate immune system.

The innate immune response, the first line of defense against invading pathogens, can be perturbed by environmental toxicants such as arsenic. This study reports the effects of arsenic on innate immunity of zebrafish. Respiratory burst activity, messenger RNA expression of tumor necrosis factor alpha (TNF-alpha), a primer of the respiratory burst response, and mRNA expression of the antiviral cytokines interferon (IFN) and MX, : before and after viral infection, were examined in arsenic-exposed zebrafish larvae. Respiratory burst activity and TNF-alpha expression were decreased upon arsenic exposure, indicating inhibition of TNF-alpha priming of the respiratory burst response. Arsenic enhanced IFN expression slightly over time, but reduced MX : expression. In zebrafish infected with snakehead rhabdovirus, arsenic decreased induction and altered the kinetics of IFN and MX : upon infection. Differences in IFN and MX : expression in arsenic-exposed larvae point toward an interruption of the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway.