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Oxidative stress response in Paracoccidioides brasiliensis: assessing catalase and cytochrome c peroxidase
Alessandra S Dantas1, Rosângela V Andrade, Maria J de Carvalho
1Departamento de Biologia Celular, Laboratório de Biologia Molecular, Universidade de Brasília, Brasília, Distrito Federal, Brazil.
Abstract:
Paracoccidioides brasiliensis is a dimorphic fungus that infects humans and establishes infection in the yeast form. We are interested in the mechanisms this fungus uses to evade the human immune system, and in its survival strategies within infected host cells. Reactive oxygen species play an important role in host defence, but are detoxified by pathogen-derived antioxidant enzymes to prevent oxidative damage. The transcriptional and post-transcriptional regulation of P. brasiliensis catalase and cytochrome-c peroxidase (CCP) antioxidant enzymes upon culture treatment with hydrogen peroxide (H(2)O(2)) is described. High H(2)O(2) concentrations (up to 100 mm) still permitted 70-100% survival of exponential and stationary phase yeast cells, though stationary phase cells were consistently more resistant. P. brasiliensis has both cytosolic and peroxisomal catalase isoenzymes and a single cytochrome-c peroxidase. High-dose treatments with H(2)O(2) led to an early increase in total catalase and CCP enzymatic activities, indicative of post-transcriptional regulation. The expression levels of the catalase genes increased three to fourfold when the cells were treated with 50 mm H(2)O(2) for 40 or 50 min. Lipid peroxidation, as assessed by the thiobarbituric acid method, was relatively low upon treatment with H(2)O(2), which was consistent with our results demonstrating that P. brasiliensis has a powerful antioxidant defence system enabling it to survive H(2)O(2)-mediated stress.
Insights
Paracoccidioides brasiliensis utilizes potent antioxidant enzymes, catalase and cytochrome-c peroxidase (CCP), to survive high hydrogen peroxide (H2O2) concentrations. This fungal defense system is crucial for evading host immune responses and establishing infection.
Area of Science:
- * Mycology
- * Immunology
- * Biochemistry
Background:
- * Paracoccidioides brasiliensis is a human-pathogenic dimorphic fungus.
- * Fungal survival within host cells involves evading immune defenses, particularly reactive oxygen species (ROS).
- * Antioxidant enzymes detoxify ROS, preventing oxidative damage.
Purpose of the Study:
- * To investigate the regulation of P. brasiliensis catalase and cytochrome-c peroxidase (CCP) in response to hydrogen peroxide (H2O2).
- * To understand the survival mechanisms of P. brasiliensis yeast cells under oxidative stress.
Main Methods:
- * Yeast cells of P. brasiliensis were cultured and treated with varying concentrations of H2O2.
- * Catalase and CCP enzymatic activities were measured.
- * Gene expression levels of catalase were analyzed.
- * Lipid peroxidation was assessed using the thiobarbituric acid method.
Main Results:
- * P. brasiliensis yeast cells exhibited high survival rates (70-100%) even at 100 mM H2O2, with stationary phase cells being more resistant.
- * Exposure to H2O2 rapidly increased total catalase and CCP enzymatic activities, indicating post-transcriptional regulation.
- * Catalase gene expression increased significantly (three to fourfold) after 40-50 minutes of exposure to 50 mM H2O2.
- * Low levels of lipid peroxidation suggested an effective antioxidant defense system.
Conclusions:
- * P. brasiliensis possesses a robust antioxidant defense system, including catalase and CCP, enabling survival under severe oxidative stress.
- * Both transcriptional and post-transcriptional mechanisms contribute to the regulation of these antioxidant enzymes.
- * This defense system is critical for P. brasiliensis to counteract host immune responses and persist within the host.
