VDR and rheumatoid arthritis: Both ATO and Vit D upregulated the expression of VDR, PPAR-γ, and LC-3 in vitro (Figure 3(a), p<0.05), but ATO had a synergistic effect with Vit D on this upregulation in RA FLS (Figure 3(a), p<0.05); low doses of ATO (1 mg/kg/d) plus Vit D (400 ng/kg/d) achieved similar effects to ATO (2 mg/kg/d) (Figures 3(a) and 4(b)).