Background and Aims
Exacerbated immune activation, intestinal dysbiosis, and a disrupted intestinal barrier are common features among inflammatory bowel disease (IBD) patients. The polyamine spermidine, which is naturally present in all living organisms, is an integral component of the human diet, and exerts beneficial effects in human diseases. Here, we investigated whether spermidine treatment ameliorates intestinal inflammation and offers therapeutic potential for IBD treatment.
Methods
We assessed the effect of oral spermidine administration on colitis severity in the T cell transfer colitis model in Rag2 -/- mice by analysis of endoscopy, histology, and molecular inflammation markers. The effects on the intestinal microbiome were determined by 16S sequencing of mouse feces. The impact on intestinal barrier integrity was evaluated in co-cultures of patient-derived macrophages with intestinal epithelial cells.
Results
Spermidine administration protected mice from intestinal inflammation in a dose-dependent manner. While T helper cell subsets remained unaffected, spermidine promoted anti-inflammatory macrophages and prevented the microbiome shift from Firmicutes and Bacteroides to Proteobacteria, maintaining a healthy gut microbiome. Consistent with spermidine as a potent activator of the anti-inflammatory molecule protein tyrosine phosphatase non-receptor type 2 (PTPN2), its colitis-protective effect was dependent on PTPN2 in intestinal epithelial cells and in myeloid cells. The loss of PTPN2 in epithelial and myeloid cells, but not in T cells, abrogated the barrier-protective, anti-inflammatory effect of spermidine and prevented the anti-inflammatory polarization of macrophages.
Conclusion
Spermidine reduces intestinal inflammation by promoting anti-inflammatory macrophages, maintaining a healthy microbiome, and preserving epithelial barrier integrity in a PTPN2-dependent manner.