Human neutrophils are targets to paracoccin, a lectin expressed by Paracoccidioides brasiliensis

Paracoccin (PCN), a lectin expressed by Paracoccidioides brasiliensis (Pb), is known to exert activities on the fungal biology, as well as different immune cells of myeloid origin. The aim of this study was to investigate the direct interaction of the recombinant form of the lectin (rPCN) with neutrophils, a neglected area.

Freshly isolated human neutrophils from healthy donors were used.

Neutrophils were incubated with rPCN in vitro.

After the treatment, the production of reactive oxygen species (ROS), DNA release, IL-8, TNF, IFN-γ, IL-10, IL-12p40, TGF-β and IL-1β production, fungicidal ability, apoptosis and de novo protein synthesis was determined.

rPCN was found to induce ROS production as well as DNA release. Using the ROS inhibitor, diphenyleneiodium, both ROS production and DNA release were significantly inhibited. In addition, rPCN was found to induce IL-8 and IL1-β production, inhibit apoptosis and induce de novo protein synthesis. Addition of cycloheximide, a protein synthesis inhibitor, drastically reversed the antiapoptotic effect of rPCN. Finally, the ability to kill Pb yeasts by human neutrophils was significantly increased after rPCN stimulation.

rPCN can alter the biology of human neutrophils increasing their fungicidal ability. Moreover, the ability of rPCN to increase DNA release and to induce suppression of neutrophil apoptosis occurs by a ROS- and de novo protein synthesis-dependent mechanism, respectively.