The role of HuR in mediating snail expression in human small airway epithelium induced by cigarette smoke extract

Abstract

Objective: To investigate the abundance of human antigen R (HuR) in small airway epithelial cells stimulated by cigarette smoke extract (CSE) as well as the role of HuR in mediating snail which is recognized as a key transcription factor in regulating epithelial-mesenchymal transition (EMT). Methods: Human small airway epithelial cells (HSAEpiC) cultured in vitro were exposed to cigarette smoke extract (CSE) to model COPD status. Real-time PCR and western blotting analysis were used in detecting HuR protein and mRNA expression in cells with CSE which were divided into 5 groups: a control group, a 1%-24 h group, a 3%-24 h group, a 1%-48 h group and a 3%-48 h group. Small interfering RNA (siRNA) transfection was used to decrease HuR abundance. HuR expression at both mRNA and protein levels was detected using Real-time PCR and Western blotting analysis respectively, and the experiment was divided into 3 groups: a control group, a transfection control group and a transfection group. Snail, E-cadherin and vimentin levels were determined using Western blotting test in cells with both CSE exposure and HuR siRNA transfection which were divided into three groups: control group, CSE group and CSE + transfection group. Results: After CSE stimulation, HuR expression was increased at both mRNA and protein levels [mRNA 1%-24 h group (1.12±0.04), 3%-24 h group (1.41±0.06), 1%-48 h group (1.26±0.05), 3%-48 h group (1.49±0.06), protein 3%-24 h group (1.35±0.08), 1%-48 h group (1.17±0.06), 3%-48h group (1.42±0.06) all P<0.05]. Compared with the control siRNA, after HuR siRNA transfection, HuR mRNA and protein levels were significantly reduced [mRNA level (0.33±0.06) vs (1.02±0.10), protein level (0.46±0.07) vs (0.97±0.06), all P<0.01]. Control siRNA transfection had no effect on HuR expression [mRNA level (1.02±0.10), protein level (0.97±0.06), all P>0.05]. After 48 h stimulation with 3% CSE, the expression of HuR (1.47±0.11), snail (1.46±0.05) and vimentin (1.56±0.05) increased and the expression of E-cadherin (0.49±0.05) decreased. After transfection and CSE stimulation, the expression of HuR (0.84±0.06), snail (1.22±0.06) and vimentin (1.11±0.09) decreased and the expression of E-cadherin (0.73±0.06) increased. (All P>0.05). Conclusions: CSE promoted the expression of HuR in human small airway epithelial cells. HuR participated in the regulation process of EMT key transcription factor snail and might regulate EMT process by this action.