COMBUSTION GENERATED SOOT PARTICLES INDUCE THE RELEASE OF IL-1 LIKE CYTOKINES BY MURINE MACROPHAGES

Particles generated by combustion comprise sub-100 nm soot particles that are often associated with adverse health effects such as asthma and cardiovascular diseases as well as lung carcer mortality. Little is known about inflammatory processes generated by combustion nanoparticles that may underlie acute and chronic airway dysfunctions. In this study, preliminary results of the effect of sub-100 nm particles on macrophages, which are involved in innate immune responses responsible of inflammation, are presented. Samples were prepared starting from collection of soot particles from fuel-rich ethylene flames by means of a vertical probe and a quartz plate. Particles collected on filters were successively dissolved in water with the help of a surfactant (dimethyl sulfoxide) and sonication for 48h to obtain a stable and homogeneous dispersion. To evaluate the molecular mechanism underlying soot particle cytotoxic activities, we used murine macrophages (J774.1 cells) and treated them with particles (dissolved in DMSO 10%; 1pg/ml-5ng/ml) for 5 hours. Cell-free supernatant was tested for the levels of IL-1? and IL-1? by means of ELISA. The administration of the sole soot particles on J774.1 cells induced a concentration-dependent release of IL-1? and IL-1?, pro-inflammatory cytokines. This effect was not associated to cell death because the addition of necrostatin (1uM), well-known necrosis inhibitor, did not alter the levels of the proinflammatory cytokines. Surprisingly, the co-administration of soot particles with lipolysaccharide (LPS), well-known pro-inflammatory insult, led to the release of IL-1? and IL-1? in an additive manner compared to the sole LPS or soot particles, implying the synergistic activities of both pro-inflammatory stimuli. Our data suggest that very low concentrations of soot particles lead to the initiation of an inflammatory process that underlies IL-1? and IL-1? release. The co-administration of LPS and soot particles further exacerbates the release of the pro-inflammatory cytokines, explaining the higher susceptibility of patients to inflammatory-based airway diseases once exposed to air pollution.