Molecular characterisation of porcine miR-155 and its regulatory roles in the TLR3/TLR4 pathways

MiR-155 plays very important roles in host inflammation and immunity. However, few studies have focused on miR-155 in livestock. In this study, the molecular characterisation of miR-155 and its functional roles in TLR3/TLR4 signalling pathways were investigated in pigs. The results indicated that miR-155 was highly expressed in the spleen and fat tissues of the pig. In PK-15 cells, miR-155 was up-regulated 4 h after LPS stimulation and up-regulated 12 h and 24 h after poly (I:C) stimulation. Furthermore, the overexpression of miR-155 significantly activated the TLR3/TLR4 signalling pathways, and the inhibition of miR-155 suppressed these pathways. Thus, miR-155 played positive regulatory roles in TLR3/TLR4 signalling pathways. Additionally, one T/C SNP of miR-155 was significantly associated with basophil percentage (BA%), absolute eosinophili value (EO) and the distribution width of the least squares mean of CD3−CD4−CD8+ T cells (DWT) in pigs. Our study offers new evidence on the immune function of miR-155 in pigs.

► MiR-155 was up-regulated by LPS and poly (I:C) stimulation. ► MiR-155 played positive regulation roles in TLR3/TLR4 pathways. ► One miR-155 SNP was significantly associated with several haematological traits.