Figure 5.

Hypoxia-inducible factor (HIF)-1α mediates the increased expression of glycogen synthase 1 (GYS1) in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs). (A–D) Effect of HIF-1α depletion on GYS1 expression and intracellular glycogen levels in RA FLSs. RA FLSs transfected with scramble or HIF1A shRNA were exposed to normoxic (21% O₂) or hypoxic conditions (1% O₂) (A,C) or stimulated with TNF-α (10 ng/ml) (B,D) for 24 h. The data are presented as the mean ± SEM of four independent experiments. (E) MH7A cells were transfected with wild-type (WT) or mutant GYS1 reporter plasmids. Approximately 48 h after transfection, the cells were exposed to 1% O₂ or TNF-α (10 ng/ml) for 24 h, and luciferase activity was measured. (F) MH7A cells were co-transfected with GYS1 reporter and HIF-1α expression plasmid, and luciferase activity was measured 48 h after transfection. The data are presented as the mean ± SD of three independent experiments. *P < 0.05, **P < 0.01 vs. healthy control or normoxia or control or CPPT-Control; ^#P < 0.05, ^##P < 0.01 vs. osteoarthritis or hypoxia + scramble or TNF-α + scramble or WT.