Avaliação do papel do óxido nítrico endógeno no crescimento do fungo Paracoccidioides brasiliensis
Data
2024-04-21
Autores
Castro, Beatriz Furue de 
Orientadores
Batista, Wagner Luiz
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Fungos do gênero Paracoccidioides são responsáveis pela paracoccidioidomicose (PCM), uma infecção fúngica sistêmica prevalente na América Latina, especialmente no Brasil. No ambiente, eles assumem uma forma de crescimento conhecida como micélio, típica dos fungos. Porém, ao serem inalados por mamíferos hospedeiros, esses fungos se transformam em sua forma patogênica, chamada levedura, aproveitando a temperatura corporal (37°C). Essa alternância entre micélio e levedura é crucial para o desenvolvimento da PCM. Seu desenvolvimento depende de fatores do hospedeiro, bem como das estratégias de adaptação do fungo, conhecidas como fatores de virulência. Estes incluem o termodimorfismo, produção de adesinas, proteases e mecanismos de detoxificação contra as espécies reativas geradas pelo sistema imunológico do hospedeiro. O óxido nítrico (NO) desempenha um papel ambíguo e essencial na relação parasita-hospedeiro. Ele atua como parte do ambiente hostil gerado pelo sistema imunológico do hospedeiro, mas também é produzido endogenamente pelos fungos, com funções fisiológicas relacionadas à proliferação celular, desenvolvimento, patogenicidade e virulência. Portanto, este estudo investigou o papel da produção endógena de NO em P. brasiliensis. Para tanto, nós utilizamos um inibidor farmacológico L-NAME (um inibidor seletivo da óxido nítrico sintase) e c-PTIO (sequestrador de NO). Os mecanismos de produção de NO em fungos ainda não foram totalmente esclarecidos, mas duas vias metabólicas são destacadas na literatura: a via dependente de arginina e a via dependente de nitrato. Embora os fungos do gênero Paracoccidiodes não apresentem genes ortólogos às NOS em seu genoma, eles possuem genes relacionados às nitrito e nitrato redutases. A ausência de genes semelhantes às NOS não implica que não haja proteínas com funções semelhantes no fungo, como evidenciado neste estudo, após exposição das células de P. brasiliensis ao L-NAME, pela redução significativa do NO endógeno, inibição do crescimento celular e da transição termodimórfica para a forma patogênica, além da modulações nos principais componentes da parede cellular (β-glucanas, quitina e mananas). Adicionalmente, foi obsevado aumento da expressão gênica do gene CSP37, relacionado à capacidade de adesão do patógeno, e interferência no crescimento celular. O c-PTIO, utilizado como sequestrador de NO, também demonstrou a importância do NO endógeno para o fungo, interferindo no crescimento celular, modulação dos componentes da parede celular e aumento da expressão gênica do gene arginase. Isso reforça a presença de mais de uma via de produção de NO no fungo. Em resumo, este estudo destaca a relevância da produção endógena de NO para a proliferação celular e modulação dos componentes da parede celular do fungo, e possivelmente na patogenicidade e virulência de P. brasiliensis.
The fungi of the genus Paracoccidioides are responsible for paracoccidioidomycosis (PCM), a prevalent systemic fungal infection in Latin America, especially in Brazil. In the environment, they assume a growth form known as mycelium, typical of fungi. However, when inhaled by mammalian hosts, these fungi transform into their pathogenic form, called yeast, taking advantage of body temperature (37°C). This switch between mycelium and yeast is crucial for PCM development. Its progression depends on host factors, as well as fungal adaptation strategies, known as virulence factors. These include thermo-dimorphism, adhesin production, proteases, and detoxification mechanisms against reactive species generated by the host's immune system. Nitric oxide (NO) plays an ambiguous and essential role in the parasite-host relationship. It acts as part of the hostile environment generated by the host's immune system but is also produced endogenously by fungi, with physiological functions related to cell proliferation, development, pathogenicity, and virulence. Therefore, this study investigated the role of endogenous NO production in P. brasiliensis. To do so, we used a pharmacological inhibitor L-NAME (a selective nitric oxide synthase inhibitor) and c-PTIO (NO scavenger). The mechanisms of NO production in fungi have not yet been fully elucidated, but two metabolic pathways are highlighted in the literature: the arginine-dependent pathway and the nitrate-dependent pathway. Although Paracoccidiodes fungi do not have orthologous NOS genes in their genome, they have genes related to nitrite and nitrate reductases. The absence of NOS-like genes does not imply that there are no proteins with similar functions in the fungus, as evidenced in this study, after exposure of P. brasiliensis cells to L-NAME, by the significant reduction in endogenous NO, inhibition of cell growth, and thermo-dimorphic transition to the pathogenic form, as well as modulations in the main components of the cell wall (β-glucans, chitin, and mannan). Furthermore, there was an increase in the gene expression of CSP37, related to the pathogen's adhesion capacity, and interference in cell growth. The c-PTIO, used as a NO scavenger, also demonstrated the importance of endogenous NO for the fungus, interfering with cell growth, modulation of cell wall components, and increased gene expression of arginase. This reinforces the presence of more than one NO production pathway in the fungus. In summary, this study highlights the relevance of endogenous NO production for cellular proliferation and modulation of fungal cell wall components, and possibly for the pathogenicity and virulence of P. brasiliensis.
The fungi of the genus Paracoccidioides are responsible for paracoccidioidomycosis (PCM), a prevalent systemic fungal infection in Latin America, especially in Brazil. In the environment, they assume a growth form known as mycelium, typical of fungi. However, when inhaled by mammalian hosts, these fungi transform into their pathogenic form, called yeast, taking advantage of body temperature (37°C). This switch between mycelium and yeast is crucial for PCM development. Its progression depends on host factors, as well as fungal adaptation strategies, known as virulence factors. These include thermo-dimorphism, adhesin production, proteases, and detoxification mechanisms against reactive species generated by the host's immune system. Nitric oxide (NO) plays an ambiguous and essential role in the parasite-host relationship. It acts as part of the hostile environment generated by the host's immune system but is also produced endogenously by fungi, with physiological functions related to cell proliferation, development, pathogenicity, and virulence. Therefore, this study investigated the role of endogenous NO production in P. brasiliensis. To do so, we used a pharmacological inhibitor L-NAME (a selective nitric oxide synthase inhibitor) and c-PTIO (NO scavenger). The mechanisms of NO production in fungi have not yet been fully elucidated, but two metabolic pathways are highlighted in the literature: the arginine-dependent pathway and the nitrate-dependent pathway. Although Paracoccidiodes fungi do not have orthologous NOS genes in their genome, they have genes related to nitrite and nitrate reductases. The absence of NOS-like genes does not imply that there are no proteins with similar functions in the fungus, as evidenced in this study, after exposure of P. brasiliensis cells to L-NAME, by the significant reduction in endogenous NO, inhibition of cell growth, and thermo-dimorphic transition to the pathogenic form, as well as modulations in the main components of the cell wall (β-glucans, chitin, and mannan). Furthermore, there was an increase in the gene expression of CSP37, related to the pathogen's adhesion capacity, and interference in cell growth. The c-PTIO, used as a NO scavenger, also demonstrated the importance of endogenous NO for the fungus, interfering with cell growth, modulation of cell wall components, and increased gene expression of arginase. This reinforces the presence of more than one NO production pathway in the fungus. In summary, this study highlights the relevance of endogenous NO production for cellular proliferation and modulation of fungal cell wall components, and possibly for the pathogenicity and virulence of P. brasiliensis.
Descrição
Citação
CASTRO, Beatriz Furue de. Avaliação do papel do óxido nítrico endógeno no crescimento do fungo Paracoccidioides brasiliensis. 2024. 82 f. Dissertação (Mestrado em Microbiologia e Imunologia) - Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, 2024.