Abstract
The study of organic/inorganic molecules with activity against intracellular fungi of the phylum Microsporidia is of critical importance. Here, for the first time, the inactivation of these parasitic fungi by porphyrins is reported. The biological effects of porphyrins (10 µM and 100 µM) on the microsporidian Nosema ceranae was investigated in honeybee hosts using cage experiments. A significant reduction in the number of spores (from 2.6 to 5 fold) was observed in Nosema-infected honeybees with a sucrose-protoporphyrin amide [PP(Asp)2] syrup diet compared to the control honeybees. PP(Asp)2 and the other porphyrin examined in vitro, TMePyP, had a direct impact on the microsporidia. Notably, neither porphyrin requires light excitation to be active against microsporidia. Moreover, microsporidia preincubated with these porphyrins exhibited decreased ability to infect honeybees. In particular, PP(Asp)2, possessing amphiphilic characteristics, exhibited significant inactivation of microsporidia, preventing the development of the microsporidia and diminishing the mortality of infected honeybees. In addition, the porphyrin-treated spores examined by scanning electron microscopy (SEM) showed morphological changes in their exosporium layers, which were distinctly deformed. Thus, we postulate that the mechanism of action of porphyrins on microsporidia is not based on photodynamic inactivation but on the destruction of the cell walls of the spores.
Highlights
Pathogenic fungi from the phylum Microsporidia are intracellular parasites found in both vertebrates and invertebrates, including honeybees
All experimental data obtained for honeybees treated with PP(Asp)[2] were compared to those obtained for the control honeybees, which were not treated with PP(Asp)[2]
From day 6, the number of N. ceranae spores among porphyrin-treated honeybees gradually decreased in comparison to the number of spores among control honeybees, which were given solely sucrose syrup (Fig. 3)
Summary
Pathogenic fungi from the phylum Microsporidia are intracellular parasites found in both vertebrates and invertebrates, including honeybees. Enterocytozoon bieneusi is recognized as one of the most opportunistic human pathogens, causing microsporidiosis, which results in potentially fatal diarrhoea and “wasting syndrome”[2,3]. The only effective medicinal treatment for the microsporidia Nosema and Enterocytozoon is the antibiotic fumagillin[7,8]. In vitro tests of these compounds against microsporidia that infect humans have been rather limited, with only a few species shown to be sensitive to these agents. Porphyrins, which are aromatic heterocyclic compounds, are ubiquitous in nature. Porphyrins are promising alternatives to conventional antibiotics and have already been shown to be effective in vitro in the photodynamic inactivation of bacteria, viruses, fungi and protozoa[14,15]. The mode of action of this inactivation is based on the formation of reactive oxygen species (ROS) by light irradiation of a porphyrin in an environment containing molecular oxygen[16,17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
