immunology of infectious and parasitic diseases - XXXVII Congress ...

INVOLVEMENT OF NOTCH AND TLR SIGNALING PATHWAYS IN THE
IMMUNE RESPONSE OF MACROPHAGES AGAINST Paracoccidioides
brasiliensis
LAVÍNIA MARIA DAL’MAS ROMERA (1) ; SANDRO ROGÉRIO DE ALMEIDA (1)
(1) Department of Clinical and Toxicological Analysis, Faculty of Pharmaceutical
Sciences, University of São Paulo
Introduction: Paracoccidioidomycosis is a systemic mycosis of deep nature
and granulomatosis, which affects preferentially the lung tissue caused by
Paracoccidioides brasiliensis, a fungus that exhibits thermal dimorphism.
Macrophages are cells that play an important role in the induction and
regulation of the immune and/or inflammatory response and important for
controlling pathogen growth. The innate immune system is crucial in the
antifungal response and macrophages are important for controlling pathogen
growth. It was recently demonstrated the importance of Notch receptors in
regulating the activity of macrophages and the immune system. Whereas Notch
signaling may be involved in modulation of macrophage function, we evaluate
the ability of P. brasiliensis to modulate the activation of this pathway. Methods
and Results: J774 macrophages pre-stimulated overnight with LPS or not were
incubed with yeast (1:1) for 24 hours (biological triplicate) followed by analysis
of Real-Time PCR (mean value of 2 -Δ∆CT ) and ELISA (mean standard deviation).
Significance test was carried out by Anova and Tukey. The transcriptional
analysis of Notch 1 revealed that there is an increased level of transcription in
24 hours, while there is a reduction of its ligand Delta 4 in 24 hours. To verify
the importance of Notch signaling, we pre-treated macrophages with a
farmacological inhibitor of g-secretase (DAPT) for 24 hours and then they were
incubed with yeast (1:1) for 4, 12 and 24 hours. We found that phagocytosis of
yeasts by macrophages become more efficient, while there was reduction of IL-
6 production and an increased TNF-a. We saw that the fungus has the ability to
promote the production of IL-6 via Notch-TLR, making us suppose that this
cytokine is important for the establishment of the disease, leading in a fungal
benefit in relation to host. Conclusion: We suggest that P. brasiliensis uses the
Notch signaling pathway as an escape mechanism. The interaction between the
yeasts with macrophages promotes the activation of this pathway, by Notch 1
receptor, inducing increased production of IL-6 cytokine important for the growth
of fungus on host, and a reduction of TNF-a, contributing to a macrophage
activity damage caused by the fungus.
Supported by FAPESP