Figure 9.

Summary of the role of AHR ligands in blocking TGFβ induced collagen deposition and myofibroblast formation in Thyroid eye disease. TGFβ signaling induces collagen 1 expression and myofibroblast formation in orbital fibroblasts. However, in the presence of an AHR ligand like FICZ, AHR binds to its ligand and then translocates to the nucleus. There, it heterodimerizes with its binding partner, ARNT. This complex activates transcription of the interstitial collagenase, MMP1. MMP1 is secreted into the extracellular matrix and degrades fibrous collagen in the extracellular space of the orbit.