Aim: This work aimed to investigate the role of M1 intestinal macrophages-derived exosomes (M1-Exo) in colitis and its mechanism.

Methods: M1 polarization of intestinal macrophages was induced in vitro, and their exosomes were extracted and identified. Thereafter, the DSS-induced colitis mouse model was built. Each mouse was given intraperitoneal injection of exosomes, and then mouse weight and DAI were dynamically monitored. In addition, the levels of cytokines were detected by ELISA. After treatment with the TLR4 inhibitor Resatorvid, the effects of M1 macrophages-derived exosomes were observed. Besides, the mouse intestinal epithelial cells were cultured in vitro for observing function of M1-Exo.

Results: M1-exo aggravated the colitis and tissue inflammation in mice, activated the TLR4 signal, and destroyed the mucosal barrier. But M0 macrophages-derived exosomes (M0-Exo) did not have the above effects. Resatorvid treatment antagonized the roles of M1-exo. Moreover, as confirmed by cellular experiments in vitro, M1-exo destroyed mucosal barrier.

Conclusion: M1-exo serve as the pro-inflammatory mediator, which can promote mouse colitis progression by activating TLR4 signal.