Objective: The pathogenesis of cerebral aspergillosis is as yet insufficiently clarified and urgently needs further examination to develop adequate counterstrategies. Since neural damage occurs not only in close proximity to the fungal hyphae our studies concentrate on a putative contribution of fungal metabolites to the induction of tissue lesions. Application of reducing agents was tested as therapeutic approach as the biochemical structure of the toxins indicate a putative neutralization of the toxins by these compounds. Methods: Astrozytic and neuronal cell lines as well as primary microglia were incubated with various fungal toxins, including gliotoxin, patulin and citrinin. Toxicity was controlled by measuring mitochondrial activity (MTS test), immunological competence was quantified as phagocytic activity. Electron microscopy studies completed the examination of toxic effects. Results: The fungal metabolites gliotoxin, patulin and citrinin were all able to affect the viability of astrocytes, neurons and microglia in a dose-dependent manner. Gliotoxin was the most potent toxin, damaging the cells already in nanomolar concentrations. Electron microscopy studies showed changes in morphology and explicit signs of apoptosis for gliotoxin-treated cells compared to mock-treated control cells. Staining with annexin and propidium iodide confirmed the dose-dependent induction of the apoptotic program by gliotoxin as well as by patulin. Furthermore, phagocytic activity of the cells incubated with gliotoxin and patulin was depressed already in subtoxic concentrations. The reducing components glutathione and DTT were both capable to neutralize the deleterious effect of gliotoxin and patulin. All cells survived otherwise toxic concentrations of the metabolites in the presence of those substances and retained their phagocytic capacity. Conclusions: Fungal metabolites were identified as putatively potent inducers of tissue damage in cerebral aspergillosis since they significantly interfere with viability of all brain cell types tested. Being secreted by Aspergillus they might affect extended regions of brain tissue. Beside direct damage the metabolites reduce the immunologic capacity of the cells by reducing their phagocytic activity. Both effects might act synergistically and contribute to the pathogenesis of cerebral aspergillosis. Reducing agents constitute promising therapeutic components as they neutralize the toxic effect of at least some of the metabolites.
Full conference title:
20th European Congress of Clinical Microbiology and Infectious Diseases
- ECCMID 20th (2010)