CARACTERIZAÇÃO ESTRUTURAL E IMUNOQUÍMICA DE GLICOINOSITOL FOSFORILCERAMIDAS DE Aspergillus fumigatus. EFEITO DE INIBIDORES DE SÍNTESE DE GLICOESFINGOLIPÍDEOS EM FUNGOS PATOGÊNICOS. / Structural and immunochemical characterization of glycosylinositol phosphorylceramides from Aspergillus fumigatus. Effect of glycosphingolipid synthesis inhibitors on pathogenic fungi.
AUTOR(ES)
Luciana Lopes Guimarães
DATA DE PUBLICAÇÃO
2006
RESUMO
The search for alternatives for new antifungal therapies led our laboratory to analyze the molecular structures of specific glycosphingolipids (GSLs) present in fungi but not in mammals. We analyze the molecular structures of glycosylinositol phosphorylceramides (GIPCs) from the opportunistic fungus Aspergillus fumigatus. GSLs were extracted and purified by a combination of ion exchange chromatography (DEAE-Sephadex), High Performance Liquid Chromatography (HPLC) and preparative High Performance Thin Layer Chromatography (HPTLC). The structures of the GIPCs from A. fumigatus were elucidated by GC/MS, and were described as: Af-2: Manpα1→3Manpα1→2InsPCer Af-3a: Galfβ1→6Manpα1→3Manpα1→2InsPCer Af-3b: Manpα1→3(Galfβ1→6)Manpα1→2InsPCer Af-3c: Manpα1→3Manpα1→6GlcpNα1→2InsPCer Af-4: Galfβ1→6Manpα1→3(Galfβ1→6)Manpα1→2InsPCer By HPTLC immunostaining, Af-3a, Af-3b and Af-4 were found to be reactive with sera of patients with aspergillosis, probably the Galf terminal residue present in these structures would represent the antigenic component recognized by the antibodies present in these sera. This is the first description of the glycan structures displayed in the GIPCs Af-3a and Af-4. The structures from Af-2 and Af-3b were previously described in P. brasiliensis (Pb-2 and Pb-1, respectively). Af-3c was previously described in S. schenckii (Ss-Y6). These results point to new directions, that could lead to the development of more efficient methodologies in the immunodiagnostic of aspergillosis, increasing the specificity of the current protocols. To better understand the importance/biological role of GSLs in different fungi, we tested inhibitors of GlcCer synthase and IPC synthase in cultures of pathogenic fungi. The addition of the inhibitor of GlcCer synthase, D-P4, was efficient in the inhibition of the growth in all of the species of fungi studied in this thesis: Paracoccidioides brasiliensis, Histoplasma capsulatum, Sporothrix schenckii and Criptococcus neoformans. The inhibitor of IPC synthase, Aureobasidin A (AbA), was also efficient in inhibition of the growth of these fungi. AbA (40μM) inhibited 100% of the colony forming of Paracoccidioides brasiliensis, Histoplasma capsulatum, and Criptococcus neoformans, however, in S. schenckii the same concentration only inhibited 50% of the colony forming. Either D-P4 or AbA were able to inhibit the yeast-mycelium transition in P. brasiliensis and H. capsulatum. The results presented here may open attractive perspectives for new antifungal therapies based on the specific inhibition of enzymes of the biosynthetic pathway of fungal GSLs.
ASSUNTO(S)
1. fungos patogênicos. 2. glicoesfingolipídeos. 3. glicoinositol fosforilceramidas. 4. glucosilceramida. 5. caracterização estrutural. 6. inibidores de síntese de glicoesfingolipídeos. ciencias da saude
