678 Biased CXCR3 ligands differentially alter allergic contact hypersensitivity and chemotaxis

Abstract

Allergic contact dermatitis (ACD) is a disease with few targeted therapies. Chemokines play an important role in ACD through the recruitment of T-cells that express the chemokine receptor (CKR) CXCR3. Chemokines signal through CKRs, a subgroup of the G proteincoupled receptor (GPCR) family, which are targeted in >30% of drugs. However, few drugs target CKRs. Classically, GPCRs were thought to act as simple switches turned on by agonists and off by antagonists. We now appreciate that GPCRs adopt multiple conformations that link to distinct signaling pathways, such as G-proteins and ß-arrestins (ßarrs). These pathways can be selectively activated by a novel class of receptor ligands, termed biased agonists, which signal through some pathways while blocking signaling through others. The purpose of this study was to determine the roles that G-proteins and ßarrs play in ACD by selectively targeting signaling with CXCR3 biased agonists. Mouse and human cell chemotaxis was determined through transwell migration, and the effects of CXCR3 ligands on ACD were assessed in the DNFB allergic contact hypersensitivity (CHS) mouse model. Patient biopsies of patch tested skin were analyzed. Our results show that ßarr signaling through CXCR3 is necessary for full efficacy chemotaxis of both mouse and human T-cells. A topically applied ßarr-biased ligand doubled (ph0.05) the CHS inflammatory response in WT, but not in ßarr2 KO or CXCR3 KO, mice. Flow cytometry of mouse skin demonstrated increased T-cells following ßarr-biased drug treatment. We conclude that CXCR3 ßarr-mediated signaling is critical for effector T-cell recruitment that underlies the inflammatory response in CHS. These findings suggest that biased ligands could be utilized to selectively target CKRs for therapeutic benefit.