Mycobacterium bovis bacille Calmette-Guérin (BCG) enhances human beta-defensin-1 gene transcription in human pulmonary gland epithelial cells.

AIM: To examine the stimulatory effect of bacille Calmette-Gu rin (BCG) cell wall components on human beta-defensin-1 (hBD-1) gene expression and analyze the response element in the 5'-flanking region of the gene.

METHODS

BCG cell wall proteins were fractionated by Sephadex G-150 chromatography. Using reverse-transcription polymerase chain reaction (RT-PCR) and Northern hybridization analysis, hBD-1 mRNA expression was detected in a human pulmonary gland epithelial cell line SPC-A-1 cells. Progressive deletions of 5'-flanking region of hBD-1 gene were produced by PCR and ligated into promoterless chloramphenicol acetyltransferase (CAT) expression plasmid to construct pCAT reporter plasmids. Reporter gene expression was determined by ELISA.

RESULTS

There was an obvious enhancement of hBD-1 mRNA expression after stimulation with heat-inactivated BCG whole cells (50 mg/L), or the cell wall components with a molecular weight of 18-30 kDa (3 mg/L) for 8 h. The upstream sequence between -314 bp and +54 bp had the inducible activity by BCG, which contained CCAAT/enhancer binding protein-beta (C/EBP beta), activator protein-1 (AP-1), and CP2 cis element.

CONCLUSION

BCG cell wall components (18-30 kDa) can stimulate hBD-1 mRNA expression in pulmonary gland epithelial cells. The sequence (-314/+54) containing C/EBP beta, AP-1, and CP2 binding sites in the upstream of hBD-1 is involved in this induction.