Type I interferon (IFNd) enhanced the innate immune response and lipid droplets (LDs) formation in obscure puffer Takifugu obscurus

As one member of type I IFN, IFNd showed huge distinctive responses and activity during the viral or bacterial infection in various fish species. Our previous study identified IFNd from obscure puffer Takifugu obscurus (ToIFNd), and the function and regulation of ToIFNd was further investigated in the present study. The transcriptional levels of ToIFNd were significantly induced post bacteria Vibrio harveyi and virus simulator Poly (I:C) stimulation in the head kidney. In addition, recombinant ToIFNd (rToIFNd) treatment enhanced the expressions of numerous interferon stimulated genes (ISGs, such as Mx1, PKR1, and PKR2) and several immune effectors (such as Il1, faslg, and tnf14) both in the in vivo and in vitro experiments. The expression patterns of interferon regulatory factors (IRFs) post rToIFNd stimulation suggesting that IRF3, 7, and 8 showed strong response and might play critical role during the ToIFNd mediated signal transduction. Remarkably, we firstly found that rToIFNd stimulation promoted lipid droplets (LDs) formation in liver, which was further confirmed by the increased number of LDs by TEM, up-regulated expressions of LDs marker PLIN3, as well as the transcripts of genes involved in the transport and synthesis of neutral lipids. These results corroborate the antibacterial and antiviral function of ToIFNd in obscure puffer, and revealed that ToIFNd might play immune regulatory role by medicating LDs formation, which will contribute to explore the functional characteristics of IFN system.