DOP013 An IBD-associated variant in PTPN2 promotes inflammatory responses but enhances the anti-inflammatory effect of spermidine

Abstract

The single-nucleotoide polymorphisms (SNP) rs1893217, located in the gene locus encoding protein tyrosine phosphatase non-receptor type 2 (PTPN2), is associated with inflammatory disorders, including inflammatory bowel disease (IBD), rheumatic arthritis, and type 1 diabetes. We have demonstrated that PTPN2 plays a crucial role in maintaining intestinal homeostasis. The polyamine spermidine, which is a potent activator of PTPN2 enzymatic activity, limits IFNg-induced pro-inflammatory signalling events via activation of PTPN2. Of note, spermidine treatment promotes intestinal barrier function and reduces intestinal inflammation in a mouse model of colitis in vivo. However, it is unclear how spermidine modulates inflammatory signalling cascades in primary immune cells from IBD patients. The aim of this study was to investigate whether spermidine treatment is effective in reducing IFNg-induced signalling in peripheral blood mononuclear cells (PBMC) from IBD patients and to investigate how the presence of the PTPN2 risk allele (SNP rs1893217) affects the outcome of spermidine treatment. PBMC were isolated from IBD patients heterozygous for SNP rs1893217 (CT; n = 4) or homozygous for the major allele (TT; n = 4), as well as from healthy controls (all TT; n = 5) and treated with INFg (100 ng/ml) and/or spermidine (10 nM). mRNA expression of INFg, PTPN2, intercellular adhesion molecule-1 (ICAM1) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2) was analysed by quantitative PCR. As expected, IFNg-treatment resulted in increased mRNA expression of the IFN-g response genes ICAM1, PTPN2, and NOD2. In PBMC from patients with the CT genotype, basal mRNA expression of those genes was already elevated, and their mRNA expression level following IFNg treatment was clearly higher than those observed in PTPN2 wild-type cells. Activation of PTPN2 by spermidine clearly ameliorated IFN-g-induced up-regulation of ICAM1, IFNG and NOD2 mRNA expression in all patients (p < 0.05). Of particular interest and despite elevated IFN-g responses, spermidine treatment was more effective in patients with the CT genotype (p < 0.05). Our results demonstrate that spermidine treatment is effective in reducing inflammatory signalling in PBMC from IBD patients. The presence of the C allele in PTPN2 SNP rs1893217 promotes inflammatory responses, but concurrently renders the cells more susceptible to the anti-inflammatory effects of spermidine. This indicates that spermidine treatment might be a promising novel therapeutic approach in IBD patients and that the C allele might serve as a good predictor for treatment response. This might be a step towards personalised medicine in the management of IBD.