Doxycycline is an antibiotic that possess anti-inflammatory properties. These anti-inflammatory properties make doxycycline an attractive candidate for possible treatments for a variety of common chronic obstructive airway diseases. Interleukin-8 (IL-8) is a major inflammatory chemokine and a powerful chemo-attractant for both neutrophils and monocytes. We hypothesized that doxycycline might exert its anti-inflammatory effects, at least in part, by modulating IL-8 production. To test this hypothesis, A549 human lung epithelial cells were stimulated with cytomix (IL-1beta, TNF-alpha and gamma-IFN) in the presence or absence of varying concentrations of doxycycline. Doxycycline decreased IL-8 protein production in a concentration- and time-dependent manner. In the presence of 30 microg/ml doxycycline IL-8 protein production was decreased by 63% through out a 30 hr time course. In chemotaxis assays monocyte and neutrophil migration was decreased by 55% and 57% respectively. Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments suggest that doxycycline does not decrease expression of IL-8 mRNA and that use of the RNA polymerase II inhibitor DRB indicates that doxycycline does not effect stability of this mRNA. In the presence of doxycycline p38-alpha mitogen-activated protein kinase (MAPK) expression is decreased by 36% in cytomix-stimulated cells. These data demonstrate that doxycycline can modulate IL-8 release and suggest that it has potential as an anti-inflammatory in those disorders where IL-8 is an important inflammatory mediator.