title: Melanin is effective in protecting fast and slow growing fungi from various types of ionizing radiation.
abstract: Melanin is a ubiquitous pigment with unique physicochemical properties. The resistance of melanized fungi to cosmic and terrestrial ionizing radiation suggests that melanin also plays a pivotal role in radioprotection. In this study, we compared the effects of densely-ionizing deuterons and sparsely-ionizing X-rays on two microscopic fungi capable of melanogenesis. We utilized the fast-growing pathogenic basiodiomycete forming an induced DOPA-melanin, Cryptococcus neoformans (CN); and the slow-growing environmental rock-inhabiting ascomycete synthesizing a constitutive DHN-melanin, Cryomyces antarcticus (CA); melanized and non-melanized counterparts were compared. CA was more resistant to deuterons than CN, and similar resistance was observed for X-rays. Melanin afforded protection against high-dose (1.5 kGy) deuterons for both CN and CA (p-values < 10-4). For X-rays (0.3 kGy), melanin protected CA (p-values < 10-4) and probably CN. Deuterons increased XTT activity in melanized strains of both species, while the activity in non-melanized cells remained stable or decreased. For ATP levels the reverse occurred: it decreased in melanized strains, but not in non-melanized ones, after deuteron exposure. For both XTT and ATP, which reflect the metabolic activity of the cells, larger and more statistically-significant differences as a function of melanization status occurred in CN. Our data show, for the first time, that melanin protected both fast-growing and slow-growing fungi from high doses of deuterons under physiological conditions. These observations may give clues for creating melanin-based radioprotectors.
authors.affiliation: Department of Ecological and Biological Science, University of Tuscia, Viterbo, Italy.|Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Pacelli
authors.affiliation: Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Bryan
authors.affiliation: Department of Ecological and Biological Science, University of Tuscia, Viterbo, Italy.
authors.forename: Silvano
authors.initials: S
authors.lastname: Onofri
authors.affiliation: Department of Ecological and Biological Science, University of Tuscia, Viterbo, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Selbmann
authors.affiliation: Center for Radiological Research, Columbia University, New York, NY, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Shuryak
authors.affiliation: Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Dadachova
mesh_terms: D003455:Cryptococcus neoformans / Q000187:drug effects* / Q000528:radiation effects*; D008543:Melanins / Q000494:pharmacology*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D014965:X-Rays
chemical_list: D008543:Melanins; D011837:Radiation-Protective Agents