Inhaled LPS induces blood release of Clara cell specific protein (CC16) in human beings

Abstract

Animal models of lung inflammation have validated the plasma 16-kd Clara cell protein (CC16) as a peripheral marker of the permeability of the alveolocapillary barrier. We investigated in human beings whether inhaled LPS induced a rise in airways permeability measured by the plasma changes in CC16. The CC16 was measured in plasma from 15 subjects exposed to LPS by inhalation, during which the kinetics and the dose-response relationship of LPS-induced CC16 were evaluated. Because LPS-induced response involves macrophages activation, the protective effect of oral methylprednisolone was also evaluated. An inhalation of 50 microg LPS induced a significant ( P < .001) rise in CC16 after 6 hours (from 7.24 [+/-0.68] microg/L to 10.69 [+/-0.99] microg/L) that normalized at 24 hours (6.65 [+/-0.33] microg/L). The CC16 response was dose-related, with the no-response threshold 0.5 microg LPS. A 6-day treatment with 20 mg/d methylprednisolone inhibited significantly ( P < .001) the CC16 response to 50 microg LPS. Exposure to LPS by inhalation in healthy subjects induces an intravascular leakage of CC16 that can be blocked by corticosteroids. These observations further validate plasma CC16 as a noninvasive test of the alveolocapillary barrier permeability.