The increase of fungal infections in the past two decades, particularly in immunocompromised patients, and the fungi resistance to conventional antifungal therapies, has raised the interest in searching new approaches in the treatment of fungal infections.
In order to analyze the fungi glycosphingolipids as targets for antifungal therapies, the effect of inhibitors of glucosylceramide (GlcCer) synthase (D-P4) and inositol phosphorylceramide synthase (Aureobasidin A) were evaluated in cultures of pathogenic fungi.
Inhibition studies were performed incubating 105 yeast forms of Paracoccidioides brasiliensis, Histoplasma capsulatum, Sporothrix schenckii and Criptococcus neoformans with D-P4 and Aureobasidin A (AbA) from 1µM up to 40 µM. After 24 hours of incubation at 37°C, cells were washed with PBS, plated on solid medium, and colony forming units were determined.
D-P4 at 10µM was highly effective in inhibiting the growth of all species of fungi studied. In a similar fashion AbA at 40µM was also effective in the inhibition of fungi growth. AbA inhibited 100% of colony formation of Paracoccidioides brasiliensis, Histoplasma capsulatum, and Criptococcus neoformans. It is noteworthy that for S. schenckii, the same concentration of AbA inhibited only 50% of the colony formation. The inhibition of GSLs biosynthesis in P. brasiliensis by D-P4 and AbA was confirmed by: i) indirect immunofluorescence with specific fungi anti-GIPC (mAb MEST-1) and anti- glucosylceramide (mAb MEST-2) and ii) inhibition of incorporation of [3H] - palmitic acid into GIPCs and glucosylceramide fractions.
It was also observed that D-P4 at 4µM and 8µM was able to inhibit 100% of the yeast-mycelium transition in H. capsulatum and P. brasiliensis, respectively. Likewise, AbA at 0.08 µM and 0.5 µM inhibited yeast-mycelium transition of P. brasiliensis and H. capsulatum, respectively.
The results presented here open new attractive perspectives for alternative antifungal therapies based on the specific inhibition of enzymes of the biosynthetic pathway of fungal GSLs.
Supported by CNPq and FAPESP