Abstract
Purpose :
Thyroid eye disease (TED) is an autoimmune process in which the connective tissue behind the eye becomes inflamed, remodeled, and enlarged. Tissue remodeling results from orbital fibroblasts (OF) activation and proliferation. Platelet-derived growth factors (PDGF) are elevated in the orbit of individuals with TED compared to non-TED patients. PDGF signaling induces OF proliferation ECM production however, the molecular mechanism(s) are unclear. PDGF signaling may be a novel therapeutic target for TED. We have previously shown that the aryl hydrocarbon receptor (AHR), a ligand activated nuclear receptor, is important in regulating OF myofibroblast formation. Here, we hypothesized that natural and synthetic ligand mediated activation of the AHR will block PDGF induced cell proliferation in TED OFs.
Methods :
Primary human OFs from TED and non-TED patients were cultured under standard conditions. OFs were treated with PDGFb, with or without the AHR ligands FICZ or tapinarof. Cell viability was measured by the AlamarBlue assay. Cell lysates were collected and analyzed by Western blotting and RT-PCR to measure PDGF and AHR signaling responses. Scratch assays were used to measure OF migration. AHR siRNA was used to determine the role of AHR in PDGF signaling.
Results :
PDGFb led to a robust increase in OF activation and migration as demonstrated through AKT phosphorylation, thymidylate synthase expression, proliferation, and cell migration. Activation of the AHR with FICZ or tapinarof blocked PDGF signaling and PDGF induced cell migration.
Conclusions :
These data reveal that targeting the AHR with naturally occurring ligands mitigate PDGF signaling in TED OFs. Further, these studies support the concept that AHR and PDGF signaling pathways are potential targets that could form the basis for new TED therapeutics.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.