Tetracycline (TCN) dose-dependently inhibits adenosine-5′-triphosphate (ATP)-induced CXCL8 and CXCL1 production of human microvascular endothelial cell line-1 (HMEC-1). (a) CXCL8: HMEC-1 cells were cultured in the presence of TCN for 30 min followed by addition of ATP to 200 μm. Supernatants were collected 24 h later and analysed for CXCL8 content. Note that ATP enhances CXCL8 release. Error bars indicate ± SD (P = 0.011, <0.001 and <0.001, respectively, for TCN 20, 40 and 80 μg/ml compared with 0 μg/ml for the ATPγS-treated groups). (b) CXCL1: HMEC-1 cells were cultured in the presence of TCN for 30 min followed by addition of ATP to 200 μm. The supernatants were collected 24 h later and analysed for CXCL1 content. Note that ATP enhances CXCL1 release. Error bars indicate ± SD (P = <0.001 for TCN 10, 20, 40 and 80 μg/ml compared with 0 μg/ml for the ATP-treated groups).