n-n--n---triacetylfusarinine-c and Pulmonary-Aspergillosis

Aspergillus fumigatus produces the siderophore triacetylfusarinine C (TAFC) for iron acquisition which is essential for its virulence. Therefore, TAFC is a specific marker for invasive aspergillosis. We have shown previously that positron emission tomography (PET) imaging with [. Fifteen TAFC derivatives were prepared and labeled with gallium-68. In vitro uptake assays were carried out in A. fumigatus under iron-replete as well as iron-depleted conditions and distribution coefficient was determined. Based on these assays, three compounds, [. In vitro uptake studies using A. fumigatus revealed specific uptake of mono- and trisubstituted TAFC derivatives at RT. Lipophilicities as expressed by logD were 0.34 to - 3.80. The selected compounds displayed low protein binding and were stable in PBS and serum. Biodistribution and image contrast in PET/X-ray computed tomography of [. Our studies show the possibility to modify TAFC without losing its properties and specific recognition by A. fumigatus. This opens also new ways for multimodality imaging or theranostics of fungal infection by introducing functionalities such as fluorescent dyes or antifungal moieties.

Topics: Animals; Aspergillus fumigatus; Blood Proteins; Ferric Compounds; Gallium Radioisotopes; Humans; Hydroxamic Acids; Mice, Inbred BALB C; Molecular Imaging; Mutation; Mycoses; Positron Emission Tomography Computed Tomography; Protein Binding; Pulmonary Aspergillosis; Rats; Siderophores; Tissue Distribution

Aspergillus fumigatus is the most common airborne fungal pathogen for humans. In this mold, iron starvation induces production of the siderophore triacetylfusarinine C (TAFC). Here we demonstrate a link between TAFC and ergosterol biosynthetic pathways, which are both critical for virulence and treatment of fungal infections. Consistent with mevalonate being a limiting prerequisite for TAFC biosynthesis, we observed increased expression of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase (Hmg1) under iron starvation, reduced TAFC biosynthesis following lovastatin-mediated Hmg1 inhibition, and increased TAFC biosynthesis following Hmg1 overexpression. We identified enzymes, the acyl-CoA ligase SidI and the enoyl-CoA hydratase SidH, linking biosynthesis of mevalonate and TAFC, deficiency of which under iron starvation impaired TAFC biosynthesis, growth, oxidative stress resistance, and murine virulence. Moreover, inactivation of these enzymes alleviated TAFC-derived biosynthetic demand for mevalonate, as evidenced by increased resistance to lovastatin. Concordant with bilateral demand for mevalonate, iron starvation decreased the ergosterol content and composition, a phenotype that is mitigated in TAFC-lacking mutants.

Topics: Amphotericin B; Animals; Aspergillus fumigatus; Biomass; Biosynthetic Pathways; Enoyl-CoA Hydratase; Ergosterol; Ferric Compounds; Gene Deletion; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Fungal; Gene Silencing; Genes, Fungal; Hydroxamic Acids; Hydroxymethylglutaryl CoA Reductases; Iron Deficiencies; Ligases; Lovastatin; Mevalonic Acid; Mice; Microbial Sensitivity Tests; Oxidative Stress; Pulmonary Aspergillosis; Pyrimidines; Siderophores; Triazoles; Up-Regulation; Virulence; Voriconazole