Objective  Based on the analysis of microRNA (miR) profile of macrophages induced by titanium dioxide, to investigate biological functions of miR-27b which is associated with immune-related pathways on macrophages RAW264.7 and regulation function of miR-27b on phosphoinositide-3-kinase, regulatory subunit 3 (Pik3r3) gene.

Method  Diana-mirPath online software and Targetscan software were used to analyze the related pathways and putative targets of miR-27b. miR-27b mimics were transfected into RAW264.7 cells in order to upregulate the expression level of miR-27b. Then cell proliferation, cell cycle, and apoptosis were examined using MTT assay and flow cytometry method. The protein expression levels of the putative targets were detected by Western blot.

Result  The results of signaling pathway and target gene analyzed by Diana-mirPath online software showed that miR-27b participated in 23 pathways -ln P≥2.99 (P<0.05), and the pathway with the highest score (16.89) was T cell receptor signaling pathway. The putative target gene results showed that Pik3r3 might be one of the target genes of miR-27b. After transfection of miR-27b mimics, there was no significant difference in optical density (D) values and cell cycles between the transfected group and the negative control group (D: P=0.725; G1: P=0.490; S: P=0.088; G2: P=0.323, respectively). Apoptosis rate of macrophages in the miR-27b mimics transfected group was significantly higher than that in the negative control group (P=0.023). Besides, compared with the negative control group, the protein expression level of Pik3r3 in the transfected group showed no significant difference (P >0.05).

Conclusion  In the present study, miR-27b could promote the apoptosis of RAW264.7, and the regulation of miR-27b need more studies.