|Budget Amount *help
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥1,800,000 (Direct Cost: ¥1,800,000)
Macrolide antibiotics are known to be effective for the treatment of chronic inflammatory airway diseases including diffuse panbronchiolitis, chronic bronchitis and bronchial asthma. Other than anti-microbial activities, macrolides have "anti-inflammatory" effects, such as the inhibition of cytokine production. In the present study, we investigated the effects of clarithromycin (CAM) on the interleukin-8 (IL-8) gene expression and its protein levels using a human bronchial epithelial cell line, BET-1A cells. Northern analyses demonstrated that CAM inhibited the tumor necrosis factor alpha (TNF)-induced IL-8 gene expression in dose and incubation time-dependent fashions. The half-life of IL-8 mRNA transcripts in TN F-treated BET-1A cells did not change with CAM.Transfection studies with BET-1A cells, using fusion genes composed of the 5'-flanking sequences of the IL-8 gene and a luciferase reporter gene, demonstrated a potent promoter activity in a 174.bp segment (-130 to +44 bp relative to the transcription start site). This segment includes AP-1 and NF-_<lambda>B-like sites, and exhibited a strongest response to TNF.TNF-induced promoter activity in this segment showed a significant repression by CAM.However, a 156-bp segment (-112 to +44 bp), which does not include an AP-1 site but includes a NF-_<lambda>B-like site, did not show a significant repression of TNF-induced promoter activity by CAM.Consistent with promoter analyses, an electrophoretic mobility shift assay demonstrated that CAM repressed the AR-1 binding in TNF-treated BET-1A cells, however, TNF induced both AP-1 and NF-_<lambda>B binding activities in BET-1A cells. These data suggest that macrolidessuch as CAM repress the IL-8 gene transcription mainly via the AP-1 binding site in human bronchial epithelial cells. Our findings provide a novel mechanism of the anti-inflammatory function of macrolides, implicating a target for the development of a new drug for the treatment of chronic airway inflammation.