ATP selectively packages TNF within microvesicles released from alveolar macrophages

Background: ATP triggers cells to release microvesicles (MVs), which play crucial roles in cellular communication by ferrying molecular cargo between cells. MVs may protect its contents from dilution, degradation or consumption, yet there is a paucity of literature examining TNF release within intra-alveolar MVs. Aims/Objectives: To investigate if ATP causes alveolar macrophages (AM) to preferentially release TNF within MVs. Methods: Primary mouse AMs were activated with 1µg/ml LPS, and then exposed to a 9second hit9 of ATP 6mM/ecto-ATPase inhibitor 1mM for 1 hour to produce MVs (identified on flow cytometry as CD11c+, Results: ATP treatment eradicated soluble TNF release from AMs (Control 107±13 pg vs ATP 4.8±6.1 pg, p Conclusion: These data show that a danger signal such as ATP, superimposed onto a pro-inflammatory stimulus, suppresses TNF release from AMs in the ordinary soluble form but preferentially packages TNF within MVs. This switch phenomenon indicates a novel mechanism of long-range TNF signalling in inflammatory lung diseases such as acute lung injury.