Neutrophil extracellular traps promote intestinal barrier dysfunction by regulating macrophage polarization during trauma/hemorrhagic shock via the TGF-β signaling pathway

The mechanism by which neutrophil extracellular traps (NETs) may cause intestinal barrier dysfunction in response to trauma/hemorrhagic shock (T/HS) remains unclear. In this study, the roles and mechanisms of NETs in macrophage polarization were examined to determine whether this process plays a role in tissue damage associated with T/HS. Rat models of T/HS and macrophage polarization were developed and the levels of NETs formation in the intestinal tissue of T/HS rats were assessed. NET formation was inhibited in models of T/HS to examine the effect on intestinal inflammation and barrier injury. The proportions of pro-inflammatory and anti-inflammatory macrophages in the damaged intestinal tissues were measured. Finally, high-throughput sequencing was performed to investigate the underlying mechanisms involved in this process. The study revealed that the level of NETs formation was increased and that inhibition of NETs formation alleviated the intestinal inflammation and barrier injury. Moreover, the number of pro-inflammatory macrophages increased and the number of anti-inflammatory macrophages decreased. RNA sequencing analysis indicated that NETs formation decreased the expression of transforming growth factor-beta receptor 2 (TGFBR2), bioinformatic analyses revealed that TGFBR2 was significantly enriched in the transforming growth factor-beta (TGF-β) signaling pathway. Verification experiments showed that NETs impeded macrophage differentiation into the anti-inflammatory/M2 phenotype and inhibited TGFBR2 and TGF-β expression in macrophages. However, treatment with DNase I and overexpression of TGFBR2, and inhibition of TGF-β promoted and prevented this process, respectively. NETs may regulate the macrophage polarization process by promoting intestinal barrier dysfunction in T/HS rats through the TGFBR2-mediated TGF-β signaling pathway.