Hypoxia and hypoxia -inducible factor 1945; modulate the response of human dendritic cells against Aspergillus fumigatus

Ref ID: 19539

Author:

M Fliesser1*, H Schlossnagel1, F Ebel2, H Einsele1, J Loeffler1

Author address:

1Medical Clinic and Policlinic II, University Hospital, Wuerzburg, Germany
2Max von Pettenkofer-Institute, Ludwigs-Maximilians-University, Munich, Germany

Full conference title:

6th Advances Against Aspergillosis 2014

Abstract:

Purpose:
Immunocompromised patients are highly susceptible for the development of fungal infections
including invasive aspergillosis (IA). In mice and men, hypoxic microenvironments are present at
sites of A. fumigatus invasive growth in the lung. Hypoxia and signalling via hypoxia-inducible factor
(HIF) 1α are known to influence functions of immune cells, including dendritic cells (DCs). DCs are
of particular importance in initiating both innate and adaptive immunity against A. fumigatus conidia
and hyphae during IA. Here, we evaluate the role of hypoxia and HIF-1α signalling in the immune
response of human DCs against A. fumigatus in vitro.
Methods:
Monocytes (CD14+/CD1a-) were isolated from PBMCs of healthy donors and differentiated into
DCs (CD14-/CD1a+) by five days incubation with IL-4 and GM-CSF. To study HIF-1α function,
DCs were electroporated with siRNA directed against HIF-1α mRNA 24 h prior to the experiments
to knock down HIF-1α . Immature DCs were stimulated with A. fumigatus germ tubes at normoxia or
hypoxia (1 % O2), followed by characterization of DC metabolism, maturation and gene expression
profile using genome-wide microarrays.
Results:
DCs consumed more glucose and released more lactate in the cell culture media when stimulated
with A. fumigatus at either normoxia or hypoxia, or when cultivated at hypoxia without stimulus, and
this switch in energy metabolism was at least in part dependent on HIF-1α . Up-regulation of relevant
maturation and co-stimulatory molecules (CD40, CD80, CD83, CD86 and HLA-DR) as well as of
the homing-receptor CCR7 was reduced on DCs stimulated with A. fumigatus at hypoxia compared
to normoxia. This effect seemed to be independent of HIF-1α , as both, HIF-1α silenced DCs and
control DCs showed similar results. Gene expression profiles of DCs stimulated with A. fumigatus
for 6 h at normoxia or hypoxia revealed a minor influence of hypoxia alone on DC gene expression
compared to stimulation with A. fumigatus at either normoxia or hypoxia. However, knock-down of
HIF-1α significantly affected gene expression in A. fumigatus stimulated DCs, leading to differential
expression of app. 250 genes at normoxia and 1000 genes at hypoxia. A first pathway analysis
suggests reduced immune functions of HIF-1α silenced DCs, indicating that this transcription factor
might be important in the immune response against A. fumigatus.
Conclusions:
Our results suggest that hypoxia and HIF-1α signaling have substantial impacts on DC function,
which might also influence the course and outcome of IA in immunocompromised patients. DC
maturation was impaired after stimulation with A. fumigatus at hypoxia compared to normoxia. In
future studies, we will evaluate the influence of hypoxia and HIF-1α signalling on the ability of DCs
to initiate a T-cell response against A. fumigatus. We will further analyze the gene expression profile
of HIF-1α silenced DCs at normoxia and hypoxia to understand the underlying pathways and the
role of this transcription factor in the response of human DCs against A. fumigatus.

Abstract Number: 66

Conference Year: 2014

Link to conference website: http://www.AAA2014.org

New link: NULL

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