Respostas transcricionais de Paracoccidioides ao estresse nitrosativo

Abstract

Paracoccidioides is a thermal dimorphic fungus that causes Paracoccidioidomycosis (PCM), an endemic disease in Latin America. Immune cells have a variety of defense mechanisms against pathogens, such as the production and release of nitric oxide (NO), one of the reactive nitrogen species (RNS). RNS react with cellular components, resulting in damage to DNA and membranes, inhibition of repiration and inactivation of cellular enzymes. To understand how Paracoccidioides responds to nitrosative stress, this study aims to identify genes that might contribute to this response. The Paracoccidioides yeast cells grouth was evaluated in the presence of various concentrations of sodium nitrite (NaNO2). The nitrosative stress was confirmed by quantification of nitrite in the cultures supernatant and by the inhibition of the cytochrome c oxidase (complex IV) activity. The transcriptional analyzes were performed by sequencing a cDNA library constructed with Paracoccidioides mRNA obtained after incubation of fungal cells with 500 µM NaNO2 during 1 h. The results show the induction of transcripts related to several cellular pathways, including genes of mitochondrial electron transport chain. The expression of selected transcripts was confirmed by quantitative real time RT-PCR. Moreover, mitochondrial activity measured by XTT method was reduced in the presence of NaNO2 during the first 2 hours of treatment. Additionally, the NADP+/NADPH ratio is lower during nitrosative stress, as demonstrated. The results suggest that the induction of transcripts associated with energy production during nitrosative stress may reflect a compensatory effect on the inhibition of enzymes that carry out this metabolic function, probably to ensure the production of energy and/or contribute to the redox balance by generation of NADPH.