Expression of RANTES by human bronchial epithelial cells in vitro and in vivo and the effect of corticosteroids.

Abstract

Recent studies have demonstrated that RANTES, a member of the CC chemokine family affecting monocytes, T cells, basophils, and eosinophils, is expressed by several cell types. To investigate whether human bronchial epithelial cells can also express this chemokine, we investigated human bronchial epithelial cells for their ability to synthesize RANTES, both in vitro and in vivo. Additionally, we investigated the effect of treatment for 4 mo with inhaled corticosteroids on the expression of RANTES in these cells in vivo. Human bronchial epithelial cells cultured from surgical tissue expressed the mRNA for RANTES and synthesized RANTES, as demonstrated by polymerase chain reaction and immunocytochemical staining and enzyme-linked immunosorbent assay, respectively. Incubation of the cultures with 50 ng/ml of tumor necrosis factor-alpha (TNF-alpha) significantly increased the release of RANTES into culture medium after 18 to 48 h of incubation, an effect that was abolished by treatment of the cultures with anti-TNF-alpha antibody. RANTES was also expressed in the bronchial epithelium in vivo, as indicated by positive immunocytochemical staining of bronchial biopsy tissues obtained from mild asthmatic patients before and after treatment with 500 micrograms of inhaled beclomethasone dipropionate (BDP) twice daily or matched placebo for 4 mo. Quantitation, by color image analysis, of the percentage of epithelium staining for RANTES showed that treatment with BDP decreased the expression of RANTES in the bronchial epithelium from 17.12% to 4.22% (P < 0.05). The numbers of EG2-staining cells in the epithelium were also reduced, from 790.1/mm2 to 203.3/mm2 (geometric mean; P < 0.01), after BDP treatment. These results suggest that human bronchial epithelial cells are capable of synthesizing RANTES and may therefore play an important role in the development of inflammation in allergic airways disease. Furthermore, corticosteroids may prevent airway inflammation by downregulating the expression of proinflammatory cytokines in the bronchial epithelium.