mycotoxins, cerebral aspergillosis

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Klinische Mykologie

Mittwoch, 27. Februar 2008, 18:00 - 18:15

Mycotoxins in cerebral aspergillosis: virulence factors and therapeutic targets

C. Speth, C. Kupfahl, M. Hagleitner, M.C. Deutinger, G. Rambach, I. Mohsenipour,

M.P. Dierich (Innsbruck, AT; Heidelberg, DE)

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Objective: The high lethality of cerebral aspergillosis urgently asks for a

deeper insight into the pathogenic mechanisms of this disease and for new

therapeutic approaches which help the local immunity in the brain to cope with

the infiltrating fungus. Therefore we studied whether secreted mycotoxins

contribute to neural damage and inefficient immune response in cerebral

aspergillosis and thus provide a putative target for a supportive antifungal

therapy.

Methods: Different Aspergillus-derived mycotoxins were tested for their effect

on the viability and proliferation of astrocytes, neurons and microglia using

MTS assays. The secretion of gliotoxin was measured using HPLC and tandem mass

spectrometry. Phagocytic activity of cells in the presence of mycotoxins was

quantified with fluorescent latex beads and subsequent microscopy; oxidative

burst was studied by FACS.

Results: Pathogenic Aspergillus species secrete a variety of mycotoxins

including patulin, gliotoxin, verruculogen, fumitremorgin C and citrinin. We

measured a direct toxic effect of these substances on astrocytes, neurons and

microglia, and could show that all mycotoxins affect their viability. Different

brain cells differed in their susceptibility towards the fungal substances with

neurons and microglia being the most sensitive cell types. In addition we

demonstrated that Aspergillus fumigatus is able to produce and secrete gliotoxin

when cultivated in cerebrospinal fluid; the produced amounts were sufficient to

induce a significant toxic effect on all brain cell types.

Furthermore, we used subtoxic concentrations of the mycotoxins to study a

putative modulation of the immunological activity of local and infiltrating

immune cell types; their dysfunction induced by the fungal compounds might

contribute to the failure in antimicrobial defence and consequently to the high

lethality. First experiments showed that infiltrating peripheral immune cells

revealed a diminished capacity of antigen presentation and phagocytosis after

incubation with the mycotoxins.

A number of neuroprotective substances is already used routinely in different

neurodegenerative diseases, or is at least tested successfully in animal models.

We performed some tests with these substances in order to protect the cells from

mycotoxin-induced damage. Carnitin proved to be the most promising compound and

could at least partly inhibit the mycotoxins-induced decrease in cell viability.

Conclusions: These data indicate an essential contribution of mycotoxins in the

pathogenesis of cerebral aspergillosis. As a therapeutic approach diverse

neuroprotective substances known to be generally effective in neurodegenerative

diseases might be used to neutralize the toxic or immune-inhibitory activity of

the mycotoxins.

http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=55124 & XNSPRACHE_ID=1 & XNKON\

GRESS_ID=65 & XNMASKEN_ID=900

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18th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID)

19.04.2008 - 22.04.2008

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Home - 20.04.2008 - Pathogenesis

Pathogenesis

Sunday, April 20, 2008, 17:48 - 18:00

Gliotoxin is an important virulence factor in cerebral aspergillosis

C. Speth, C. Kupfahl, M. Hagleitner, M. Deutinger, G. Rambach, I. Mohsenipour,

M.P. Dierich (Innsbruck, AT; Heidelberg, DE)

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Objective: The high lethality of cerebral aspergillosis urgently asks for a

deeper insight into the pathogenic mechanisms of this disease. Therefore we

studied whether mycotoxins, especially gliotoxin, contribute to neural damage

and to the inefficient immune response in cerebral aspergillosis. Furthermore we

tested the putative capacity of antioxidant components to interfere with the

harmful activity of gliotoxin.

Methods: The secretion of gliotoxin after fungal growth in cerebrospinal fluid

(CSF) was measured using HPLC and tandem mass spectrometry. An effect of

gliotoxin on the viability and proliferation of astrocytes, neurons and

microglia was tested by MTS assays. Phagocytic activity of cells in the presence

of gliotoxin was quantified using fluorescent latex beads and subsequent

microscopic analysis; oxidative burst was studied by FACS.

Results: Pathogenic Aspergillus species like A.fumigatus secrete significant

levels of gliotoxin when cultivated in CSF. The corresponding concentration of

gliotoxin was sufficient to affect the viability of astrocytes, neurons and

microglial cells, with neurons and microglia being the most sensitive cell

types. Subtoxic concentrations of gliotoxin diminished the capacity of microglia

to phagocyte pathogens. Furthermore gliotoxin exaggerated the oxidative burst in

infiltrating granulocytes induced by stimuli such as PMA.

Therapeutic approaches might aim to neutralize the inhibitory or even toxic

effect of gliotoxin and thus to reconstitute the potency of cerebral immunity.

We used glutathione for this purpose, a tripeptide made up from cysteine,

glutamate and glycin which act as a reducing compound. In first promising

experiments with glutathione we were able to protect brain cells from gliotoxin

concentrations which otherwise were shown to kill the cells. Furthermore

glutathione reconstituted the phagocytic activity of immune cells in the

presence of gliotoxin.

Conclusions: These data indicate an essential contribution of gliotoxin to the

pathogenesis of cerebral aspergillosis. As a therapeutic approach

neuroprotective substances such as glutathione might be used to neutralize the

toxic or immune-inhibitory activity of gliotoxin.

http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=55830 & XNSPRACHE_ID=2 & XNKON\

GRESS_ID=73 & XNMASKEN_ID=900

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