Novel roles of chloroquine and hydroxychloroquine in Graves’ orbitopathy therapy by targeting orbital fibroblasts

Context: Graves’ orbitopathy (GO) causes infiltrative exophthalmos by inducing excessive proliferation, adipogenesis and glycosaminoglycan production in orbital fibroblasts (OFs). Interference with OF autophagy is a potential therapy for proptosis.

Objectives: Here, we aimed to evaluate the effects of chloroquine (CQ) and hydroxychloroquine (HCQ), the autophagy inhibitors commonly used in clinical practice, on OFs.

Design/Setting/Participants: OFs isolated from patients with GO (GO-OFs) or control persons (non-GO-OFs) were cultured in proliferation medium (PM) or subjected to differentiation medium (DM). OFs were treated with CQ or HCQ (0, 2, 5,10 μM), and subsequently examined in vitro.

Main Outcome Measures: CCK-8, EdU incorporation and flow cytometry assays were used to assess cellular viability. Adipogenesis was assessed with Western blot analysis, real-time PCR, and Oil Red O staining. Hyaluronan production was determined by real-time PCR and ELISA. Autophagy flux was detected using RFP-GFP-LC3 fluorescent staining and Western blot analysis.

Results: CQ/HCQ halted proliferation and adipogenesis in GO-OFs in a concentration-dependent manner through blockage of autophagy, which were not detected in non-GO-OFs. Besides, inhibitory effect of CQ/HCQ on hyaluronan secretion of GO-OFs was also concentration-dependent, mediated by downregulation of hyaluronan synthase 2 (HAS2) rather than hyaluronidases. Moreover, CQ (10 mM) induced GO-OFs apoptosis without aggravating oxidative stress.

Conclusions: The antimalarials CQ/HCQ affect proliferation, adipogenesis and hyaluronan generation in GO-OFs by inhibiting autophagy, providing proof of concept that they can treat GO as autophagy inhibitors.