Objective To investigate the effect of dopamine on lipopolysaccharide (LPS)-induced inflammatory response in mouse peritoneal macrophages (MPMs).Methods MPMs were isolated after injection of thioglycolate broth into the peritoneal cavity.MPMs from wild type C57 mice were distributed into control group,LPS group,dopamine pretreatment group,dopamine D1-like and and D2-like receptor antagonist groups (D1 and D2 antagonist groups).In the latter two groups,MPMs were pretreated with Dl-like and D2-like receptor antagonist respectively for 30 min,and then stimulated with dopamine and LPS.MPMs from wild type (TLR4 +/+) and TLR4 knock-out (TLR4-/-) mice were only divided into LPS group and dopamine pretreatment group.In LPS group,MPMs were stimulated with 1 μg/ml LPS for 6 h.In dopamine pretreatment group,MPMs were pretreated with 10-4 mol/L dopamine for 2 h,and then stimulated with 1μg/ml LPS for 6 h.Expressions of TLR4 and pro-IL-1βwere detected by Western blot and tumor necrosis factor-α (TNF-α) in cell culture supernatant by ELISA method.Results (1) Expressions of TLR4,pro-IL-1β and TNF-α in control group were (0.56 ± 0.07),(0.65 ± 0.11) and (1,770.6 ±448.8) pg/ml;in LPS group were (1.12 ± 0.15),(1.24 ± 0.20) and (15,569.5 ± 822.7) pg/ml;in dopamine pretreatment group were (0.28 ± 0.11),(0.22 ± 0.08) and (7,800.7 ±862.6)pg/ml;in D1 antagonist group were (0.25 ±0.12),(0.18 ±0.09) and (7,065.0 ± 1016.8)pg/ml;in D2 antagonist group were (0.80 ±0.09),(0.44 ±0.08) and (14,299.6 ± 1430.9)pg/ml.The three indicators in LPS group were increased compared to control group and dopamine pretreatment group (P ＜ 0.05),and in D2 antagonist group were increased compared to dopamine pretreatment group (P ＜ 0.05).There were no obvious differences between D1 antagonist group and dopamine pretreatment group(P ＞0.05).(2) After LPS stimulation,expressions of pro-IL-1 β and TNF-α in TLR4+/+ mice were (0.94 ±0.17) and (15,109.0 ± 1,903.4)pg/ml,and were (0.08 ±0.04) and (5,063.6 ± 512.8) pg/ml in TLR4-/-mice (P ＜0.05).After dopamine pretreatment,expressions of proIL-1β and TNF-α were (0.45 ±0.12) and (6,383.9 ± 1,287.3) pg/ml in TLR4+/+ mice,and were (0.05 ± 0.02) and (4,863.0 ± 824.7) pg/ml in TLR4-/-mice.Expressions of pro-IL-1β and TNF-o were higher in TLR4 +/+ mice than in TLR4-/-mice after LPS stimulation (P ＜ 0.05).Expressions of pro-IL-1β and TNF-αin TLR4 +/+ mice were reduced after dopamine pretreatment compared to LPS stimulation (P ＜ 0.05),while were similar in TLR4-/-mice (P ＞ 0.05).Conclusion Dopamine can inhibit LPS-induced inflammatory response in MPMs,and the inhibition is strongly related to dopamine D2-1ike receptor and TLR4.