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Background5-Nitro-2-(3-styrene-acrylic amine) benzoic acid ( NPPB),a chloride channel inhibitor,has a promoting effect on cell apoptosis in myocardial ischemia and reperfusion of domestic rabbit.The CIC chloride channel has been found in the ocular trabecular cells.However,the effect of NPPB on the shape and function of trabecular cells is unclear. Objective This study was performed to investigate the effect of NPPB on the proliferation,cell cycle progression and apoptosis of human trabecular meshwork cells.MethodsThe immortalized human trabcular cell strain was cultured,and logarithmic-phase cells were incubated in 96-well plates at a density of 1 ×106/ml.Different concentrations of NPPB (10,50,100 μ mol/L) were added to the medium,and the MTT assay was used to assess the growth and proliferation of the cells.Flow cytometry was used to evaluate the cell cycle.Then,100 mg/L 5-FU or 100 mg/L 5-FU + 100 μmol/L NPPB was used to induce cell apoptosis,which was assessed by Annexin V-PI.The membrane potential of mitochondria was examined using rhodamine 123 (△ψm).Results After 48 hours of treatment with NPPB,the abosorbency (A value) of the cells was gradually lowered with the increasing dose of NPPB,with significant differences among the 4 groups (F =7.230,P =0.006).Compared with the 10 μmol/L NPPB group,the A values were significantly declined in the 50 and 100 μmol/L NPPB groups (t =1.610,P =0.025 ;t =12.270,P =0.001 ).Forty-eight hours after exposure to NPPB,the percentage of cells in G0/G1 phase was increased and that in the S phase was decreased.The percentages of cells in different phases of cell cycle were significantly different in comparison with their control groups (without NPPB)( P＜0.05 ).Twenty-four and 48 hours after the treatment with 100 mg/L 5-FU,the apoptosis rates of the cells were raised in the 100 mg/L 5-FU group and 100 mg/L 5-FU + 100 μmol/L NPPB group compared to the without NPPB group (t24h =2.130,P =0.023;t48h =4.810,P=0.011 ) ;while that in the 100 mg/L 5-FU+100 μmol/L NPPB group was higher than the 100 mg/L 5-FU group ( t24 h =1.980,P =0.037 ; t48 h =1.290,P =0.028 ),and the mitochondrial membrane potential was lowered ( t24h =1.580,P =0.029 ; F48 h =6.200,P =0.015 ).Conclusions NPPB suppresses the proliferation of human trabecular cells and promotes the cells to enter S phase via the G1/S check point.In addition,ClC might be involved in an anti-apoptosis mechanism through the internal mitochondrial pathway.