Objective      To determine the effect of chloroquine (CQ) on the expression of ubiquitin-proteasome system (UPS)-related molecules A20

TRIM33 and USP28 in LPS-stimulated Raw264.7 cells and the role of A20 in CQ-pretreated activated Raw264.7 cells.       Methods      The mRNA expression levels of zine finger protein A20

E3 ubiquitin ligase TRIM33 and ubiquitin-specific protease USP28 in CQ-pretreated LPS-activated Raw264.7 cells were measured by real-time PCR

and Western blotting was used to detect these protein expressions. siRNA transfection was used to silence A20

and TNF-α mRNA expression in CQ-pretreated LPS-activated Raw264.7 cells was tested by real-time PCR.       Results      The mRNA expression levels of A20

TRIM33 and USP28 in CQ-pretreated activated Raw264.7 cells were significantly increased compared with LPS treatment only (3.197±0.013 vs 1.292±0.009

1.627±0.113 vs 0.797±0.083

1.387±0.144 vs 0.742±0.061

P0.05). The protein expression levels of A20 and TRIM33 in CQ-treated cells were significantly increased. TNF-α mRNA expression was up-regulated in CQ-pretreated cells after siRNA interference of A20 (7.650±0.113 vs 4.145±0.120

P0.01).       Conclusion      CQ effectively enhances the mRNA and protein expression levels of A20

TRIM33 and USP28 in LPS-activated macrophages

and mRNA expression of TNF-α is significantly increased in LPS-activated Raw264.7 cells upon interference with A20

which indicates that UPS may play a role in the inhibitory effect of CQ on activating LPS-TLR4 signaling pathway.