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Assessing Anti-fungal Activity of Isolated Alveolar Macrophages by Confocal Microscopy
Published on: July 9, 2014
Extracellular Vesicles from Candida haemulonii var. vulnera Modulate Macrophage Oxidative Burst
Bianca T M Oliveira1, Thales M H Dourado2, Patrick W S Santos1
1Department of Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil.
Abstract:
Members of the Candida haemulonii species complex are multidrug-resistant emergent yeast pathogens able to cause superficial and invasive infections in risk populations. Fungal extracellular vesicles (EVs) play a critical role in the pathogenicity and virulence of several species and may perform essential functions during infections, such as carrying virulence factors that behave in two-way communications with the host, affecting survival and fungal resistance. Our study aimed to describe EV production from Candida haemulonii var. vulnera and evaluate whether murine macrophage RAW 264.7 cells respond to their stimuli by generating an oxidative response after 24 h. For this purpose, reactive oxygen species detection assays demonstrated that high concentrations of yeast and EVs (1010 particles/mL) of Candida haemulonii did not change macrophage viability. However, the macrophages recognized these EVs and triggered an oxidative response through the classical NOX-2 pathway, increasing O2•- and H2O2 levels. However, this stress did not cause lipid peroxidation in the RAW 264.7 cells and neither lead to the activation of the COX-2-PGE2 pathway. Thus, our data suggest that low concentrations of C. haemulonii EVs are not recognized by the classical pathway of the oxidative burst generated by macrophages, which might be an advantage allowing the transport of virulence factors via EVs, not identified by the host immune system that could work as fine tube regulators during infections caused by C. haemulonii. In contrast, C. haemulonii var. vulnera and high EV concentrations activated microbicidal actions in macrophages. Therefore, we propose that EVs could participate in the virulence of the species and that these particles could be a source of antigens to be exploited as new therapeutic targets.
Insights
Candida haemulonii extracellular vesicles (EVs) trigger macrophage oxidative responses, potentially aiding fungal virulence. These EVs may offer novel therapeutic targets against multidrug-resistant yeast infections.
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- The *Candida haemulonii* species complex comprises multidrug-resistant yeast pathogens causing significant human infections.
- Fungal extracellular vesicles (EVs) are implicated in virulence, mediating host-pathogen interactions and carrying effector molecules.
- Understanding EV roles in *C. haemulonii* infections is crucial for developing effective treatments.
Purpose of the Study:
- To characterize EV production by *Candida haemulonii* var. *vulnera*.
- To investigate the response of murine macrophage RAW 264.7 cells to *C. haemulonii* EVs, specifically focusing on oxidative stress generation.
Main Methods:
- Production and isolation of extracellular vesicles from *Candida haemulonii* var. *vulnera*.
- Assessment of macrophage viability upon exposure to yeast and EVs using reactive oxygen species (ROS) detection assays.
- Evaluation of the involvement of the NOX-2 and COX-2-PGE2 pathways in the macrophage response to EVs.
Main Results:
- High concentrations of *C. haemulonii* yeast and EVs did not compromise macrophage viability.
- Macrophages recognized *C. haemulonii* EVs, triggering an oxidative response via the NOX-2 pathway, increasing superoxide and hydrogen peroxide levels.
- This oxidative stress did not induce lipid peroxidation or activate the COX-2-PGE2 pathway; however, *C. haemulonii* var. *vulnera* and high EV concentrations activated microbicidal actions.
Conclusions:
- Low concentrations of *C. haemulonii* EVs may evade classical macrophage recognition, facilitating virulence factor delivery.
- EVs produced by *C. haemulonii* var. *vulnera* and high EV concentrations can stimulate microbicidal activity in macrophages.
- Fungal EVs represent potential virulence factors and promising sources of antigens for novel therapeutic strategies against *C. haemulonii* infections.
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