OBJECTIVETo explore the mechanism of signal transduction in respiratory syncytial virus (RSV)-induced expression of thymic stromal lymphopoietin (TSLP) in bronchial epithelial cells.

METHODSThe eukaryotic expression vector of RSV F protein, pcDNA3-F, was constructed and transfected into in vitro cultured human bronchial epithelial cell line CRL-9483, which was also transfected with Smad7 expression vector pcDNA3/Smad7 or exposed to p38, ERK1/2, JNK, and JAK/STAT1 inhibitors. The mRNA levels of TSLP and the housekeeping GAPDH gene were analyzed 24 h later with semi-quantitative RT-PCR. In cells with downregulated TSLP mRNA expression due to the addition of the signal inhibitors, cytoplasm TSLP or GAPDH protein levels were further analyzed using Western blotting.

RESULTSVirtually no TSLP mRNA expression was detected by RT-PCR in cultured CRL-9483 cells transfected with pcDNA3 exclusively (TSLP/GAPDH relative total gray scale of 0.10-/+0.03), while cell transfection with pcDNA3-F resulted in significantly increased TSLP mRNA level (0.42-/+0.20, P=0.024). In the presence of F protein expression, both p38 and JNK inhibitors could downregulate TSLP mRNA levels (0.14-/+0.04, P=0.036; 0.23-/+0.07, P=0.048, respectively), while TGF-beta-Smad inhibiting protein Smad7 (0.60-/+0.25), ERK 1/2 inhibitor (0.45-/+0.23), and JAK/STAT1inhibitor (0.44-/+0.25) failed to block TSLP expression (P>0.05). Western blotting showed that p38 inhibitor (TSLP/GAPDH relative total gray scale=3.67-/+1.18, P=0.018) and JNK inhibitor (1.48-/+0.77, P=0.004) also downregulated the protein levels of TSLP as compared with pcDNA3-F transfection group (8.13-/+2.20).

CONCLUSIONRSV F protein can stimulate TSLP expression in human bronchial epithelial cells mediated partially by p38 and JNK signal pathways.