Compound C exerts a therapeutic effect on Graves' orbitopathy via AMPK‑independent pathways

Abstract

Compound C is an adenosine monophosphate‑activated protein kinase (AMPK) inhibitor, which is also recognized as a broad‑spectrum kinase inhibitor with anti‑proliferative effects. The present study investigated the therapeutic effects of a high concentration of compound C on Graves' orbitopathy (GO) pathogenesis beyond the AMPK‑dependent pathway using human orbital fibroblasts. Orbital connective tissue was obtained from patients with GO and healthy controls, and primary orbital fibroblasts were cultured. The cells were then pretreated with a non‑cytotoxic concentration of compound C, and stimulated with either IL‑1β or TGF‑β. Pro‑inflammatory cytokine expression, profibrotic protein production and adipogenesis were evaluated using western blotting and Oil Red O staining. Adipocyte differentiation following knockdown of the hippocampal signaling pathway was also analyzed. Hyaluronan secretion was assessed using ELISA. Notably, treatment with a non‑cytotoxic concentration of compound C (10 µM) significantly suppressed AMPK and yes‑associated protein (YAP) phosphorylation in orbital fibroblasts. In addition, compound C suppressed IL‑1β‑induced pro‑inflammatory cytokine production and TGF‑β‑induced profibrotic protein production, as well as the phosphorylation of Akt, SMAD 1/2/3, and hyaluronan secretion. Similar to compound C treatment, silencing YAP and transcriptional co‑activator with PDZ‑binding motif, significantly attenuated adipogenesis as determined by Oil Red O quantification and the production of adipogenic markers. It may be hypothesized that a high concentration of compound C suppresses inflammation, fibrosis and adipogenesis in orbital fibroblasts through YAP inactivation, since YAP knockdown effectively reduced adipogenesis in GO orbital fibroblasts. Taken together, these findings suggested that compound C may exert its therapeutic effects through an AMPK‑independent mechanism, inhibiting inflammation, adipogenesis and fibrosis in orbital fibroblasts.

Keywords: GO; adipogenesis; compound C; fibrosis; inflammation.