Polarization of mouse macrophages towards M1 and M2b types induced by outer membrane vesicles derived from Proteus mirabilis
To investigate whether bacterial outer membrane vesicles(OMVs)secreted by the conditionally pathogenic bacterium Proteus mirabilis have the function of inducing macrophage polarization to regulate the tumor microenvironment,the mouse macrophage RAW264.7 was stimulated with the OMVs to detect macrophage polarization-related phenotype.The OMVs were isolated,extracted and then characterized using transmission electron microscopy.The OMVs were traced with PKH67 fluorescent dye,and the uptake of OMVs by RAW264.7 cells was observed by using fluorescence microscopy.The total NO content secreted by RAW264.7 cells and the expression of polarization-associated factors in RAW264.7 cells were detected by using total nitric oxide(NO)detection kit and real-time fluorescence quantitative PCR(RT-qPCR),respectively.The results showed that OMVs could be taken up by RAW264.7 cells,induced an increase in NO secretion in these cells,and up-regulated the expression of IL-10,IL-1β,TNF-α,and IL-6,i.e.,the occurrence of M1-type and M2b-type polarizations,which activated anti-tumor activity of macrophages.The above results suggest a potential role of OMVs secreted by P.mirabilis in the bacterium's resistance to breast tumor growth and lung metastasis.
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