Transcriptomic analysis reveals that mTOR pathway can be modulated in macrophage cells by the presence of cryptococcal cells.

Alícia C Piffer,Guido Lenz,Bruno César Feltes,Charley C Staats,Lívia Kmetzsch,Rafael De Oliveira Schneider,Marilene H Vainstein,Alexandra Gerber,Marcos P Thomé,Ana Tereza R Vasconcelos,Uriel Perin Kinskovski,Francine M Dos Santos,Augusto Schrank,Ane Wichine Acosta Garcia,Camila Diehl

doi:10.1590/1678-4685-gmb-2020-0390

Abstract

Cryptococcus neoformans and Cryptococcus gattii are the etiological agents of cryptococcosis, a high mortality disease. The development of such disease depends on the interaction of fungal cells with macrophages, in which they can reside and replicate. In order to dissect the molecular mechanisms by which cryptococcal cells modulate the activity of macrophages, a genome-scale comparative analysis of transcriptional changes in macrophages exposed to Cryptococcus spp. was conducted. Altered expression of nearly 40 genes was detected in macrophages exposed to cryptococcal cells. The major processes were associated with the mTOR pathway, whose associated genes exhibited decreased expression in macrophages incubated with cryptococcal cells. Phosphorylation of p70S6K and GSK-3β was also decreased in macrophages incubated with fungal cells. In this way, Cryptococci presence could drive the modulation of mTOR pathway in macrophages possibly to increase the survival of the pathogen.

Highlights

The worldwide incidence of cryptococcosis is approximately 220,000 cases per year, with mortality rates of 80% (Rajasingham et al, 2017)
To evaluate the changes that Cryptococcal cells induce in the transcriptional profile of macrophages, IFN-γ- and LPSactivated J774.16 macrophage-like cells were co-cultured with the fungal cells for 6 h before RNA-seq was performed
The main observed effect may be due to cryptococcal presence in the medium rather than in the intracellular compartment of macrophage cells, despite the higher phagocytosis rate of C. neoformans H99 compared to C. gattii R265 cells (Figure S1)

Summary

Introduction

The worldwide incidence of cryptococcosis is approximately 220,000 cases per year, with mortality rates of 80% (Rajasingham et al, 2017). The disease is initiated with the inhalation of basiodiospores or desiccated cells from environmental sources and subsequent interaction with alveolar phagocytic cells, such as macrophages, dendritic cells and neutrophils (Osterholzer et al, 2009; Brown, 2011) These mammalian cells engulf the pathogen and expose the yeast to damaging agents, such as low pH, reactive oxygen species, nitric oxide, as well as proteases, to kill the invading pathogen (Ghosn et al, 2006; Leopold Wager et al, 2016). C. gattii fungal cells can deregulate the maturation of dendritic cells causing suboptimal T cell activation and proliferation (Huston et al, 2013) Such pathogenic yeasts can modulate macrophage polarization to M2 (alternatively activated), thereby evading recognition and killing by the host (Leopold Wager et al, 2016). Even with the elucidation of several mechanisms showing that cryptococcal cells modulate the immune system (Leopold Wager et al, 2016; Casadevall et al, 2018), there are still points to be studied and clarified in this field

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Conclusion