Objective To investigate the inhibitory effect of erythromycin on the TNE-α release of human macrophages stimulated by cigarette smoke and its possible mechanism. Methods The human monocytic cell line U937 cells were differentiated into human macrophages by Phorbol esters (PMA). The cigarette smoke extract (CSE) (0.1, 1 , 2.5% ) and erythromycin (EM) (0. 1 , 1 , 10 μg/mE) were used to deal with the macrophages at different time points (24. 48, and 72 h) , respectively, and we chose the time and concentrations with the least effect on proliferation activity of macrophages. The 1 μg/mL CSE, 1% EM and 24-hour treatment time were selected for the experiment. The differentiated L’937 cells were randomly divided into four groups; die control group (with no intervention) , CSE group ( 1% CSE stimulation for 24 h) , CSE + EM group ( pre-incubation with 1 μg/ml EM for 24 h before 1% CSE stimulation for 24 h) , and TSA group (TSA stimulation for 24 h). The TNF-α level in the culture supernatants was measured by ELISA; Western blotting was used to measure the expression of the histone deacetvlase-1 ( HDAC1) and NE-kB protein. Results The level of TNE-α in die culture supernatants of the control group, CSE group, and CSE + EM group were (274. 96 ± 182. 39) , (744. 46 ± 638.38), and (646.57 ±603.53) pg/mL, respectively (all P <0.05). Compared with the control group, the expressionof HDAC1 protein in the CSE group, EM + CSE group, and TSA group decreased, and the expression of NF-κB protein increased (all P <0. 05). Compared with the CSE group, die expression of HD AC 1 protein increased, and die expression of NE-κB protein decreased in the EM + CSE group ( both P < 0. 05 ). Compared with the EM + CSE group, the expression of HDAC1 protein in the TSA group decreased, and the expression of NE-kB protein increased (both P <0. 05). Conclusions EM inhibits die release of TNE-α ol human macrophages induced by cigarette smoke. The mechanism is that EM may restore the expression of HDAC1 and inhibit the expression of NE-kB, which decreases the release of TNE-α and thus alleviates the inflammatory response. [ABSTRACT FROM AUTHOR]