Immune and xenobiotic response crosstalk to chemical exposure by PA01 infection in the nematode Caenorhabditis elegans

Most organisms simultaneously face various chemical and biological stresses in the environment. Herein, we investigated how pathogen infection modifies an organism's response to chemical exposure. To explore this phenomenon, we conducted a toxicity study combined with pathogen infection by using the nematode Caenorhabditis elegans, the pathogen Pseudomonas aeruginosa, and various environmental chemicals. C. elegans preinfected with PA01, when subsequently exposed to chemicals, became sensitized to the toxicity of nonylphenol (NP) and cadmium (Cd), whereas they became tolerant to the toxicity of silver nanoparticles (AgNPs); this led us to conduct a mechanistic study focusing on AgNP exposure. A gene expression profiling study revealed that most of the immune response genes activated by PA01 infection remained activated after subsequent exposure to AgNPs, thereby suggesting that the acquired tolerance of C. elegans to AgNP exposure may be due to boosted immunity resulting from PA01 preinfection. Further, a functional genetic analysis revealed that the immune response pathway (i.e., PMK-1/p38 MAPK) was involved in defense against AgNP exposure in PA01-preinfected C. elegans, thus suggesting immune and stress response crosstalk to xenobiotic exposure. This study will aid in the elucidation of how pathogen infection impacts the way the defense system responds to subsequent xenobiotic exposure.