Low oxygen helps thyroid eye disease fibroblasts resist ferroptosis and drives orbital scarring
Lab study finds hypoxia and lactate make thyroid eye disease fibroblasts resist ferroptosis and turn fibrotic. Targeting both may curb orbital scarring.
Resumo
Thyroid eye disease (TED) causes progressive scarring of the tissues behind the eye, driven by orbital fibroblasts. This lab study tested whether low oxygen, which is present in TED orbits, helps these cells resist ferroptosis, an iron-dependent form of cell death, and whether this fuels fibrosis. Fibroblasts from TED patients already carried higher levels of the protective proteins GPX4 and SLC7A11 than control cells, and low oxygen strengthened this effect. Hypoxia alone raised collagen, fibronectin and α-SMA and amplified TGF-β effects. Hypoxia also increased lactate, which itself boosted GPX4 and fibrotic markers. In hypoxic TED cells, low-dose RSL3 (a ferroptosis inducer) reduced fibrotic markers, and the glycolysis inhibitor 2-deoxy-D-glucose restored RSL3 sensitivity. The findings are cell-based and preclinical, but they suggest a combined metabolic and ferroptosis-targeting strategy worth testing.
Resumo Detalhado
Thyroid eye disease is an autoimmune condition in which orbital fibroblasts overproduce collagen and fibronectin, causing lasting tissue remodeling. Current lab models mostly use TGF-β under normal oxygen, even though TED orbits appear hypoxic (the authors previously found higher HIF-1α in patient orbital tissue). This study asked whether hypoxia pushes these fibroblasts toward resistance to ferroptosis, and whether that resistance supports fibrosis.
The team isolated primary orbital fibroblasts from 11 TED patients (euthyroid, no recent steroids or immunosuppressants) and 6 controls. Cells were exposed to graded oxygen (21% down to 1%) for 24 hours. Ferroptosis sensitivity was assessed through ROS, mitochondrial membrane potential, viability, and the proteins SLC7A11, GPX4 and ACSL4. Fibrosis was assessed through COL1A1, α-SMA, fibronectin, immunofluorescence and scratch-migration assays. They also used HIF-1α overexpression, the ferroptosis inducer RSL3, the inhibitor liproxstatin-1, exogenous lactate, and the glycolysis inhibitor 2-deoxy-D-glucose.
TED fibroblasts and tissues showed higher GPX4 and SLC7A11 (and NRF2) than controls, and TED cells generated less ROS in response to RSL3. Lowering oxygen progressively increased SLC7A11 and GPX4 and decreased ACSL4, peaking at 1% O₂; HIF-1α overexpression under normal oxygen raised SLC7A11 and GPX4. Hypoxia alone raised fibronectin, TIMP1, ITGB1, COL1A1 and α-SMA and accelerated wound closure; combined with TGF-β1 it produced the highest collagen and fibronectin levels. Under normal oxygen, RSL3 increased fibrotic markers in both cell types. Under hypoxia, however, RSL3 at 50–100 nM lowered fibrotic markers in TED cells, with the effect lost at 150 nM where viability fell; liproxstatin-1 attenuated the RSL3 effects. Hypoxia raised intracellular lactate, and lactate alone increased GPX4 and fibrotic activation, while 2-deoxy-D-glucose lowered lactate, restored RSL3 sensitivity and reduced fibrotic readouts.
The authors propose a hypoxia–lactate–GPX4 axis that makes TED fibroblasts ferroptosis-resistant and more profibrotic, and that combining metabolic inhibition with carefully dosed ferroptosis induction could restrain fibrosis. The window is narrow, since higher RSL3 doses were cytotoxic.
Caveats are substantial: all data come from cultured cells, sample sizes are small (often 3–6 lines), the controls include mixed tissue sources, and some conclusions rest on a single time point. Mitochondrial assays showed no clear oxygen-dependent difference, and the causal role of lactate and GPX4 was inferred from pharmacologic tools rather than genetic knockdown. Clinical benefit in patients is untested.
Principais Descobertas
- TED orbital fibroblasts show baseline ferroptosis resistance, with higher GPX4 and SLC7A11 and lower ACSL4 than control fibroblasts.
- Graded hypoxia (down to 1% O₂) progressively intensified this antiferroptotic profile and independently raised COL1A1, α-SMA and fibronectin without TGF-β.
- Hypoxia plus TGF-β1 produced the highest collagen and fibronectin expression, suggesting hypoxia amplifies TGF-β profibrotic signaling.
- In hypoxic TED cells, 50–100 nM RSL3 reduced fibrotic markers; 150 nM lost the effect as viability declined.
- Hypoxia raised lactate, which upregulated GPX4 and fibrosis; 2-deoxy-D-glucose lowered lactate and restored RSL3 sensitivity.
Metodologia
Primary orbital fibroblasts from 11 TED patients and 6 controls were exposed to graded hypoxia (21–1% O₂) for 24 hours. Readouts included Western blot, qPCR, immunofluorescence, ROS, JC-1, viability and scratch assays, with RSL3, liproxstatin-1, lactate, 2-deoxy-D-glucose and HIF-1α overexpression as perturbations. Statistics used t-tests and one-way ANOVA with Tukey's test.
Limitações do Estudo
Findings come from small numbers of cultured primary cell lines, with mixed control tissue sources, short 24-hour exposures and no in vivo validation. Lactate and GPX4 causality relies on pharmacology rather than genetic manipulation, the RSL3 therapeutic window is narrow with cytotoxicity at higher doses, and mitochondrial readouts were inconclusive.
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