Tetanus toxin-sensitive VAMP-related proteins are present in murine macrophages

The light chain of tetanus neurotoxin (TeTx) is a zinc endopeptidase specific for VAMP/synaptobrevin (VAMP), a 120-amino-acid integral protein previously described in the small synaptic vesicles of neuronal cells. TeTx has been shown to be active also on nonneuronal cells. By SDS-PAGE and quantitative immunoblotting on proteins derived from murine macrophages (Mphi) exposed to TeTx, we have shown that: (1) VAMP-related proteins are also present in Mphi and (2) such proteins are sensitive to TeTx proteolytic cleavage. The demonstration that TeTx acts on VAMP-related proteins also in Mphi offers a new and useful tool for molecular studies on Mphi exocytosis.

Differential susceptibility of yeast and hyphal forms of Candida albicans to macrophage-derived nitrogen-containing compounds

Candida albicans is a dimorphic fungus capable of transition from the yeast form (Y-Candida) to the hyphal form (H-Candida). Both Y-Candida and H-Candida are known to be growth inhibited by murine macrophages (M phi) in vitro. In the present report, we demonstrate that M phi exposed to interferon gamma (IFN-gamma) plus lipopolysaccharide (LPS) show enhanced anti-Y-Candida and anti-H-Candida activities. To further investigate the phenomenon, Y-Candida and H-Candida were assessed for susceptibilities to M phi-derived supernatants. Only the growth of H-Candida, and not that of Y-Candida, is impaired by cell-free supernatants from M phi treated with IFN-gamma plus LPS. In contrast, no H-Candida growth inhibition occurs when supernatants from M phi exposed to IFN-gamma plus LPS in the presence of NG-monomethyl-L-arginine, an inhibitor of nitric oxide (NO) synthesis, are employed. Finally, supernatants from M phi incubated with sodium nitroprusside, an NO-generating agent, also show anti-H-Candida activity. In conclusion, these results indicate that H-Candida but not Y-Candida is susceptible to extracellular antifungal mechanisms employed by M phi, which likely involve stable nitrogen-containing compounds.

Differential susceptibility of yeast and hyphal forms of Candida albicans to proteolytic activity of macrophages

The dimorphic transition of Candida albicans from the yeast (Y-Candida) to the hyphal (H-Candida) form is a complex event whose relevance in fungal pathogenicity is still poorly understood. Using a cloned macrophage (M phi) cell line (ANA-1), we have previously shown that a M phi can discriminate between the two fungal forms, eliciting different secretory responses. In the present study, we investigated the susceptibility of Y-Candida and H-Candida to M phi proteolytic activity. In particular, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) techniques were employed to analyze the patterns of lyticase proteinaceous extracts from cell walls of Y-Candida and H-Candida which had been unexposed or exposed to ANA-1 M phis for 3 h. Silver staining allowed detection of a complex protein pattern in both forms of C. albicans, qualitatively and quantitatively differing from each other, mainly at molecular masses below 106 kDa. Western blot staining with anti-C. albicans mannan antibodies and convalescent-phase sera of mice previously infected systemically or intracerebrally with C. albicans showed that, after contact with M phis, Y-Candida but not H-Candida proteinaceous cell wall components are profoundly modified, with substantial reduction and/or disappearance of many bands. Our experimental approach provides initial insights into the differential susceptibility of Y-Candida and H-Candida to the proteolytic activity of M phis.