Cryptococcus neoformans capsule protects cell from oxygen reactive species generated by antimicrobial photodynamic inactivation

Abstract

Antimicrobial photodynamic inactivation (APDI) is based on the utilization of substances that can photosensitize biological tissues and are capable of being activated in the presence of light. Cryptococcus neoformans is an yeast surrounded by a capsule composed primarily of glucoronoxylomannan that plays an important role in its virulence. This yeast causes infection on skin, lungs and brain that can be associated with neurological sequelae and neurosurgical interventions, and its conventional treatment requires prolonged antifungal therapy, which presents important adverse effects. The aim of this study was to evaluate the protective effect of Cryptococcus neoformans capsule against reactive oxygen species generated by APDI. Cryptococcus neoformans KN99α, which is a strain able to produce capsule, and CAP59 that does not present capsule production were submitted to APDI using methylene blue (MB), rose bengal (RB), and pL-ce6 as photosensitizers (PS). Then microbial inactivation was evaluated by counting colony form units following APDI and confocal laser scanning microscopy (CLSM) illustrated localization as well as the preferential accumulation of PS into the fungal cells. C. neoformans KN99α was more resistant to APDI than CAP59 for all PSs tested. CLSM showed incorporation of MB and RB into the cytoplasm and a preferential uptake in mitochondria. A nuclear accumulation of MB was also observed. Contrarily, pL-ce6 appears accumulated in cell wall and cell membrane and minimal florescence was observed inside the fungal cells. In conclusion, the ability of C. neoformans to form capsule enhances survival following APDI.

Effective photodynamic treatment of Trichophyton species with Rose Bengal

“…Susceptibility to Rose Bengal-PDT has been previously linked to a heightened sensitivity to oxidation of ergosterol in the fungal cell membrane, leading to further increased uptake after membrane disruption [14]. Other studies have also shown the localisation of Rose Bengal within mitochondria of yeast [24] and vacuoles of melanoma cells [25], indicating multiple sites of potential cell damage.…”

In Vitro Photodynamic Inactivation of Cryptococcus neoformans Melanized Cells with Chloroaluminum Phthalocyanine Nanoemulsion

“…The susceptibility of the fungus to PDI was associated with cell wall integrity. Prates et al (68) reported that C. neoformans capsule protects cell from oxygen reactive species generated by PDT with methylene blue, rose bengal and pL-ce6.…”

“…Prates et al. (68) reported that C. neoformans capsule protects cell from oxygen reactive species generated by PDT with methylene blue, rose bengal and pL‐ce6.…”

Light treatments of nail fungal infections

“…It has been suggested that the phototoxic action of RB is limited only to the cell membrane, as its polar nature restricts its intracellular accumulation . However, there is also evidence of intracellular RB accumulation, including the vacuoles of T. rubrum and mitochondria of Cryptococcus neoformans via fluorescence imaging . SEM imaging has also shown evidence of RB causing intracellular morphological changes to human melanoma cells, including vacuolization and mitochondrial distortion, thus supporting its ability to accumulate within cells .…”