Abstract: Objective To study the regulatory effect of Cheng's Juanbi Decoction (JBT) on autophagy in rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and role of PI3K/Akt/mTOR signaling axis in the mechanism mediating this effect. Methods CCK8 assay was used to determine the optimal concentration and treatment time of JBT for inhibiting the viability of RA- FLS. The effect of freeze-dried powder of JBT, RAPA, or both on morphology of the autophagosomes in RA-FLS was observed under transmission electron microscope, and the changes in the number of autophagosomes and autolysosomes were observed with autophagy double-labeled adenovirus experiment. RT-qPCR and Western blotting were used to detect the expression levels of the related indicators. Results The results of CCK8 assay showed that treatment with 0.5 mg/mL JBT for 12 h produced the optimal effect for inhibiting RA-FLS viability. Observation with transmission electron microscope and the results of the autophagy double-labeled adenovirus experiment both showed the presence of a small number of autophagosomes in control RA-FLS group, and treatment with JBT significantly increased the number of autophagosomes and lowered the number of autophagolysosomes in the cells. Compared with the control cells and the cells treated with JBT or RAPA alone, the cells treated with both JBT and RAPA showed significantly decreased mRNA levels of PI3K, Akt and mTOR (P<0.01) but without significant changes in their protein expressions (P>0.05); the combined treatment significantly inhibited the protein expressions of p-PI3K, p-Akt, p-mTOR, and P62 (P<0.05) and upregulated the protein expressions of Beclin-1 and LC3B (P<0.05) in the cells. Conclusion JBT can inhibit the survival rate of RA-FLS and increase the level of autophagy possibly through a mechanism that down-regulates PI3K/Akt/mTOR signaling pathway

Key words: Cheng's Juanbi Decoction; fibroblast-like synoviocytes; autophagy; PI3K/Akt/mTOR