Cell Survival and Altered Gene Expression Following Photodynamic Inactivation of Paracoccidioides brasiliensis

• Published in: Photochemistry and photobiology 2012-07, Vol.88 (4), p.992-1000
• Main Authors: Almeida, Luciane M., Zanoelo, Fabiana F., Castro, Kelly P., Borissevitch, Iouri E., Soares, Célia M. A., Gonçalves, Pablo J.
• Format: Article
• Language: English
• Subjects: Apoptosis; Colony Count, Microbial; Cytotoxicity; Dose-Response Relationship, Drug; Fungal infections; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Gene expression; Gene Expression Regulation; Light; Microbial Viability - drug effects; Microbial Viability - radiation effects; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Oxidative stress; Oxidative Stress - drug effects; Oxidative Stress - radiation effects; Oxidoreductases - genetics; Oxidoreductases - metabolism; Paracoccidioides - drug effects; Paracoccidioides - metabolism; Paracoccidioides - radiation effects; Paracoccidioides brasiliensis; Photodynamic therapy; Photosensitizing Agents - chemistry; Photosensitizing Agents - pharmacology; Porphyrins - chemistry; Porphyrins - pharmacology; Reactive Oxygen Species - agonists; Reactive Oxygen Species - metabolism; Transcription, Genetic
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/j.1751-1097.2012.01112.x

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidioides brasiliensis. Currently, the treatment approach involves the use of antifungal drugs and requires years of medical therapy, which can induce nephrotoxicity and lead to resistance in yeast strains. Photodynamic inactivation (PDI) is a new therapy capable of killing microorganisms via the combination of a nontoxic dye with visible light to generate toxic reactive oxygen species (ROS). We investigated the phototoxic effect of 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridinio)porphyrin (TMPyP), a cationic porphyrin, on the survival of P. brasiliensis following exposure to light. Phototoxicity was found to depend on both the fluence and concentration of the photosensitizer (PS). Although the biological effects of PDI are known, the molecular mechanisms underlying the resultant damage to cells are poorly defined. Therefore, we evaluated the molecular response to PDI‐induced oxidative stress by gene transcription analysis. We selected genes associated with the high‐osmolarity glycerol (HOG)‐mitogen‐activated protein kinase (MAPK) pathway and antioxidant enzymes. The genes analyzed were all overexpressed after PDI treatment, suggesting that the oxidative stress generated in our experimental conditions induces antioxidant activity. In addition to PDI‐induced gene expression, there was high cell mortality, suggesting that the antioxidant response was not sufficient to avoid fungal mortality. This is an in vitro study on the phototoxic effect of the 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridinio)porphyrin (TMPyP) in Paracoccidioides brasiliensis, a human pathogenic fungus, which causes systemic mycoses called paracoccidoidomycosis. The results suggest that TMPyP is an effective sensitizer for photoinactivation treatment and that the oxidative stress generated under our experimental conditions greatly induces antioxidant activity in P. brasiliensis cells. These results are important to the development of therapeutic tools that could be applied in vivo.