Antifungal Activity, Toxicity, and Membranolytic Action of a Mastoparan Analog Peptide

Abstract

Invasive fungal infections, such as cryptococcosis and paracoccidioidomycosis are associated with significant rates of morbidity and mortality. Cryptococcosis, caused by Cryptococcus neoformans, is distributed worldwide and has received much attention as a common complication in patients with HIV. Invasive fungal infections are usually treated with a combination of amphotericin B and azoles. In addition, 5-fluorocytosine (5-FC) is applied in cryptococcosis, specifically to treat central nervous system infection. However, host toxicity, high cost, emerging number of resistant strains, and difficulty in developing new selective antifungals pose challenges. The need for new antifungals has therefore prompted a screen for inhibitory peptides, which have multiple mechanisms of action. The honeycomb moth Galleria mellonella has been widely used as a model system for evaluating efficacy of antifungal agents. In this study, a peptide analog from the mastoparan class of wasps (MK58911) was tested against Cryptococcus spp. and Paracoccidioides spp. In addition, peptide toxicity tests on lung fibroblasts (MRC5) and glioblastoma cells (U87) were performed. Subsequent tests related to drug interaction and mechanism of action were also performed, and efficacy and toxicity of the peptide were evaluated in vivo using the G. mellonella model. Our results reveal promising activity of the peptide, with an MIC in the range of 7.8–31.2 μg/mL, and low toxicity in MRC and U87 cells (IC50 > 500 μg/mL). Taken together, these results demonstrate that MK58911 is highly toxic in fungal cells, but not mammalian cells (SI > 16). The mechanism of toxicity involved disruption of the plasma membrane, leading to death of the fungus mainly by necrosis. In addition, no interaction with the drugs amphotericin B and fluconazole was found either in vitro or in vivo. Finally, the peptide showed no toxic effects on G. mellonella, and significantly enhanced survival rates of larvae infected with C. neoformans. Although not statistically significant, treatment of larvae with all doses of MK58911 showed a similar trend in decreasing the fungal burden of larvae. These effects were independent of any immunomodulatory activity. Overall, these results present a peptide with potential for use as a new antifungal drug to treat systemic mycoses.

2-Hydroxychalcone as a Potent Compound and Photosensitizer Against Dermatophyte Biofilms

“…Intracellular ROS production after treating T. rubrum ATCC 28189 with 2-chalcone in the dark and 2-chalcone mediated PDT was evaluated using 50 µM H2DCFDA (2.7 dichlorodihydrofluorescein diacetate, Invitrogen) as described by Singulani et al (2019). This compound is converted to a highly fluorescent 2ʹ, 7ʹdichlorofluorescein (DCF) compound after cleavage of its acetate group by intracellular esterases and this compound binds to ROS.…”

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

“…, Cryptococcus spp. [32,33,[45][46][47][48][49][50][51], Aspergillus spp. [13,29,35,[52][53][54][55][56][57][58][59][60][61], Mucorales [62][63][64], Madurella mycetomatis [65][66][67], and other fungal agents [68][69][70].…”

“…The potential use of G. mellonella for evaluation of treatment efficacy has also been highlighted in several studies that focused on the development of new molecules with antifungal activities against Cryptococcus spp. [32,46,[48][49][50].…”

“…Beside plants, animals are also a source of natural compounds with antimicrobial activity. In this context, an antimicrobial peptide analogue isolated from the wasp venom was tested for its anticryptococcal activity [50]. In this study the peptide was active in vitro against C. neoformans, had low toxicity toward mammalians cells, and increased survival in a G. mellonella model of cryptococcosis.…”

Overview of Antifungal Drugs against Paracoccidioidomycosis: How Do We Start, Where Are We, and Where Are We Going?

“…Both compounds are inhibitors of the ergosterol biosynthesis, indicating that this molecular target is very promising. Antimicrobial peptides have also been proposed as potent inhibitors of Paracoccidioides spp., such as MK58911, a peptide analogue of mastoparan, which presented an MIC of 7.8 μg/mL against P. brasiliensis and 15.6 μg/mL against P. lutzii [ 44 ]. Lactoferrin-derived peptides presented MIC values between 0.63 and 1.25 μg/mL [ 45 ].…”