Toll Like Receptor 9 Pathway Mediates Schlafen+-MDSC Polarization During Helicobacter-Induced Gastric Metaplasias

Abstract

Background and AimsA subset of MDSCs that express murine Schlafen4 (SLFN4) or its human ortholog SLFN12L polarize in the Helicobacter-inflamed stomach coincident with intestinal or spasmolytic polypeptide-expressing metaplasia (SPEM). We propose that individuals with a more robust response to damage-activated molecular patterns (DAMPs) and increased Toll-like receptor (TLR9) expression are predisposed to the neoplastic complications of Helicobacter infection. MethodsA mouse or human Transwell co-culture system comprised of dendritic cells (DCs), 2-dimensional gastric epithelial monolayers and Helicobacter were used to dissect the cellular source of interferon (IFN) in the stomach by flow cytometry. Conditioned media from the cocultures polarized primary myeloid cells. Myeloid-derived suppressor cell (MDSC) activity was determined by T cell suppression assays. In human subjects with intestinal metaplasia or gastric cancer, the rs5743836 TLR9T>C variant was genotyped and linked to TLR9, IFN and SLFN12L expression by immunohistochemistry. NF{kappa}B binding to the TLR9 C allele was determined by electrophoretic mobility shift assays. ResultsHelicobacter infection induced gastric epithelial and plasmacytoid DC expression of TLR9 and IFN. Co-culturing primary mouse or human cells with DCs and Helicobacter induced TLR9, IFN secretion and SLFN+-MDSC polarization. Neutralizing IFN in vivo mitigated Helicobacter-induced SPEM. The TLR9 minor C allele creates an NF{kappa}b binding site associated with higher levels of TLR9, IFN and SLFN12L in Helicobacter-infected stomachs that correlated with a greater incidence of metaplasias and cancer. ConclusionTLR9 plays an essential role in the production of IFN and polarization of SLFN+-MDSCs upon Helicobacter infection. Subjects carrying the rs5743836 TLR9 minor C allele are predisposed to neoplastic complications if chronically infected.