Immune responses in the Japanese pufferfish (Takifugu rubripes) head kidney cells stimulated with particulate silica

Studies on immune response to crystal silica in mammals indicate immune stimulation effect of environmental parameters including silica or asbestos, but there is no information on this aspect in lower vertebrates. Therefore, we examined expression of cytokine genes related to innate immunity in the Japanese pufferfish, Fugu (Takifugu rubripes) head kidney (HK) cells stimulated with particulate silica at 10 and 50 μg mL−1. Expression of eleven cytokine genes was analyzed by the multiplex RT-PCR method (GenomeLab Genetic Analysis System, GeXPS; Beckman Coulter Inc.). Additionally, to confirm functionality of activated inflammatory immunity, we assessed phagocytic activity. Expression of NLR family genes as potential sensor molecules of inflammasome and inflammasome-associated genes (ASC and caspase-1) was also confirmed in HK cells by quantitative real-time PCR (qRT-PCR). As a result, an increased gene expression of pro-inflammatory cytokines (IL-6, IL-17A/F3, TNF-α, TNF-β and IFN-γ) and other cytokines (IL-4/13A, IL-4/13B, Type I-IFN) was recorded in particulate silica stimulated HK cells. Moreover, phagocytic activity showed a tendency to significantly increase in stimulated monocyte of HK cells after 6 h. Expression of NLR-C9 and NLR-C12 genes significantly increased in silica-stimulated HK cells. The particulate silica also significantly induced expression of inflammosome-associated genes, which may relate to the induced NLR-Cs.