The role of miR-122 in macrophage functions

• Main Authors: Yi-Ru Su, 蘇意茹
• Other Authors: Chuen-Miin Leu
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/47868227921956524374

碩士 === 國立陽明大學 === 微生物及免疫學研究所 === 102 === MicroRNAs (miRNAs) are endogenously non-coding RNAs involved in posttranscriptional gene repression. Although miR-122 is considered as a dominant liver-specific miRNA, previous studies revealed that Mir122-null mice have increased numbers of Kupffer cells, monocytes, and neutrophils in the liver. Our previous results showed that injection of LPS in mice resulted in a significantly higher serum IL-6 in the Mir122-/- mice than that in wild type (WT) mice. We hypothesize that macrophages may express Mir122, and miR-122 may regulate macrophage functions. Here we confirmed that serum IL-6 was significantly higher in Mir122-/- mice than in WT controls after injection of LPS. However, there were no differences in the cell numbers and in the percentages of peritoneal macrophages between Mir122-/- and WT mice. A low level of miR-122 was detected in the peritoneal macrophages. The addition of LPS stimulated higher IL-6 production by purified peritoneal Mir122-/- macrophages. We observed that the phagocytosis ability was similar between Mir122-/- and WT macrophages. We also examined markers for M1 and M2 macrophages, and our analysis showed that Mir122-deficent macrophages were not biased toward M1 polarization. Since NF-κB is one of the major transcription factors regulating the expression of inflammatory cytokines, we examined the effect of miR-122 on NF-κB activity by reporter assay. We found that Mir122-/- macrophages had higher NF-κB activity than WT macorphages. Several genes in the NF-κB pathway contain miR-122 target sites and we identified that they are true targets by reporter assay. Consistent with this observation, the expreesion of two target genes was higher in the Mir122-/- macrophages than the expression of those in WT. In summary, our findings suggest that miR-122 may negatively regulate the NF-κB pathway and help fine-tune the immune response.