Objective To investigate the inhibitory effect of exogenous carbon monoxide-releasing molecule 3 (CORM-3) on activation of the renal dendritic cells (rDCs) and the underlining mechanism. Methods Kidneys harvested from C57BL/6J mice were made into single cell suspension. CD11c + rDCs were then sorted by magnetic cell sorting (MACS) and the purity was assessed by flow cytometry.The rDCs were treated by CORM-3 or inactive CO-releasing molecule (iCORM) together with lipopolysaccharides (LPS). The expression of TLR4 gene was detected by quantitative real-time PCR. TNF-α protein levels in the rDCs culture were determined by ELISA. In addition, TLR4-/-(C3H/HeJ) or TLR4+/+(C3H/HeN) mice were subjected to 30 min bilateral kidney ischemia and 24-h cold preservation. The rDCs were then isolated to detect the expression of TNF-α gene in cells by quantitative real-time PCR. Results CORM-3 significantly inhibited the expression of TLR4 mNRA in immature rDCs in a dose-dependent manner(P<0.05). Compared with iCORM, CORM-3 significantly suppressed the expression of TNF-α in rDCs after LPS stimulation (P<0.01); however, this inhibitory effect of CORM-3 was abrogated in TLR4-/-mice. ConclusionCORM-3 can greatly inhibit TLR4 expression in immature rDCs,and it can also suppress proinflammatory cytokine expression induced by LPS stimulation or ischemia and cold preservation, but not in TLR4 knockout mice, suggesting that CORM-3 suppresses rDCs activation through TLR4 pathway.