ANP-NPRA Signaling Modulates Immunity By Altering TLR-2 Expression In Human Dendritic Cells (DCs)

Abstract

RATIONALE: The interaction between atrial natriuretic peptide (ANP) and its receptor (atrial natriuretic peptide receptor (NPRA) in DCs was reported to modulate immunity, but the mechanism remains poorly understood. Since toll-like receptor-2 (TLR-2) plays an important role in shaping innate immune response, the role of TLR-2 in ANP signaling was assessed in DCs. METHODS: The presence of TLRs and the signal protein, MyD88, was detected in pANP transfected DC lysates by immunoblotting, and secreted cytokines were assayed using the Bio-Plex array system. Cytokines were also measured in pANP-transfected DCs where TLR-2 expression was blocked by siTLR-2. TLR-2 interaction with NPRA was examined in TLR-2-transfected HEK 293 cells and NPRA and TLR-2 colocalization and protein-protein interaction was investigated by using immunohistochemistry and immunoprecipitation, respectively. RESULTS: ANP-NPRA signaling upregulates TLR-2 expression and downregulates MyD88 in DCs compared to controls. Treatment of pANP-transfected DCs with NPRA inhibitor isatin leads to an upregulation of IL-10. Also, pANP-transfected DCs treated with siTLR-2 show upregulation of IL-10, suggesting that TLR-2 is involved with NPRA signaling. Colocalization studies indicate that NPRA and TLR-2 are expressed together on the surface of HEK293 cells. CONCLUSIONS: These results indicate that ANP regulation of innate immunity in human DCs may involve TLR-2 signaling.