[Knockdown of Kruppel like factor 4 (KLF4) promotes RAW264.7 macrophages into M1 polarization]

Objective To investigate the effects of Kruppel like factor 4 (KLF4) gene knockdown on the polarization of RAW264.7 macrophages. Methods KLF4 knockdown lentiviral vector was constructed by RNA interfering. The lentiviral vector was transfected into RAW264.7 cells to realize stable KLF4 gene silencing in RAW264.7 cells. Interleukin-4 (IL-4) was used to stimulate macrophages in wild type group, KLF4 knockdown group and negative control group. The mRNA expression of inducible nitric oxide synthase (iNOS), IL-1β, tumor necrosis factor α (TNF-α) and Arg1, IL-10, transforming growth factor β (TGF-β) of the cells was detected by reverse transcription-PCR. Immunocytochemical staining was used to detect and localize iNOS and Arg1 protein in RAW264.7 cells. Results Levels of iNOS and IL-1β mRNA in RAW264.7 cells were significantly raised, while levels of Arg1, IL-10 and TGF-β mRNA were significantly reduced after KLF4 gene knockdown. Levels of KLF4, Arg1, IL-10 and TGF-β mRNA went up, while the relative levels of iNOS, IL-1β and TNF-α mRNA went down in wild-type RAW264.7 cells after IL-4 intervention. After shKLF4 group was intervened by IL-4, levels of iNOS, IL-1β and TNF-α mRNA in shKLF4 group (lentivirus group) were lower than those in wild-type group and higher than those in negative control group. Levels of Arg1, IL-10 and TGF-β mRNA in shKLF4 group after IL-4 treatment were higher than those in wild-type group, while Arg1 and IL-10 were lower than those in negative control group. Compared with wide-type group, the expression of iNOS protein significantly decreased, while Arg1 protein significantly increased in shKLF4 group 12 hours after IL-4 treatment. Conclusion Knockdown of KLF4 promotes the polarization of RAW264.7 macrophages into M1 as well as inhibits their polarization into M2.