Dexamethasone enhances invasiveness ofAspergillusfumigatus conidia and fibronectin expression in A549 cells

• Published in: 中华医学杂志：英文版 2013 (17), p.3289-3294
• Main Author: LI Tao LI Jing-chao QI Qian LI Yu
• Format: Article
• Language: English
• Subjects: A549细胞; Western印迹; 侵袭性; 分生孢子; 地塞米松; 糖皮质激素; 纤维连接蛋白; 荧光定量RT-PCR
• ISSN: 0366-6999; 2542-5641

Background The efficacies of current treatments for invasive aspergillus （IA） are unsatisfactory and new therapeutic targets or regimens to treat IA are urgently needed. Previous studies have indicated that the ability of conidia to invade host cells is critical in IA development and fibronectin has a hand in the conidia adherence process. In the clinical setting, many patients who receive glucocorticoid for extended periods are susceptible to Aspergillus fumigatus （A. fumigatus） infection, for this reason we investigated the effect of glucocorticoid on conidia invasiveness by comparing the invasiveness of A. fumigatus conidia in the type II human alveolar cell line （A549） cultured with different concentrations of dexamethasone. We also explored the relationships between dexamethasone and fibronectin expression. Methods Following culture with anti-fibronectin antibodies and/or dexamethasone, type II human alveolar A549 cells were infected with conidia of A. fumigatus. After 4 hours, the extracellular free conidia were washed away and the remaining immobilized conidia were released using Triton-X 100 and quantified by counting the colony-forming units. The invasiveness of conidia was measured by calculating the invasion rate （%）. The transcription of the fibronectin gene in cells cultured with different concentrations of dexamethasone for 24 hours was tested by fluorogenic quantitative RT-PCR while the expression of fibronectinin cells cultured for 48 hours was tested by Western blotting and immunocytochemistry. Results A significant reduction in the invasiveness of conidia was seen in the cells cultured with anti-fibronectin antibody （（14.42±1.68）% vs. （19.17±2.53）%, P 〈0.05）, but no significant difference was observed in cells cultured with a combination of anti-fibronectin antibody and dexamethasone （6.37×10^-5 mol/L）. There was no correlation between the dexamethasone concentration and the invasiveness of conidia after dexamethasone pretreatment of cells for 4 hours. In contrast, after pretreated for 24 hours, the invasiveness of conidia in the presence of 6.37×10^-5 mol/L dexamethasone （（24.66±2.41）%） was higher than for the control （（19.17±2.53）%） and the 0.25×10^-5 mol/L group （（19.93±3.06）%）, and the invasiveness in the 1.27×10^-5 mol/L group （（22.47±2.46）%） was also higher than in the control, P 〈0.05. The relative transcripts of the fibronectin gene after exposure to 6.37× 10^-5 mol/L dexamethasone （9.19×10^-3±1.2×10^-3） was higher than for the co