Antimicrobial activity and mechanism of action of a thionin-like peptide from Capsicum annuum fruits and combinatorial treatment with fluconazole against Fusarium solani

TAVEIRA, GABRIEL B.; CARVALHO, ANDRÉ O.; REGENTE, MARIANA; DE LA CANAL, LAURA; RODRIGUES, ROSANA; MELLO, ÉRICA O.; PINEDO, MARCELA; GOMES, VALDIRENE M.

BIOPOLYMERS

JOHN WILEY & SONS INC

Año: 2017

0006-3525

Many Fusarium species are able to cause severe infections in plants as well as inanimals and humans. Therefore, the discovery of new antifungal agents is of paramountimportance. CaThi belongs to the thionins, which are cationic peptides with lowmolecular weights (~ 5 kDa) that have toxic effects against various microorganisms.Herein, we study the mechanism of action of CaThi and its combinatory effect withfluconazole (FLC) against Fusarium solani. The mechanism of action of CaThi wasstudied by growth inhibition, viability, plasma membrane permeabilization, ROSinduction, caspase activation, localization and DNA binding capability, as assessed withSytox green, DAB, FITC-VAD-FMK, CaThi-FITC and gel shift assays. Thecombinatory effect of CaThi and FLC was assessed using a growth inhibition assay.Our results demonstrated that CaThi present a dose dependent activity and at the higherused concentration (50 μg mL-1) inhibits 83% of F. solani growth, prevents theformation of hyphae, permeabilizes membranes, induces endogenous H2O2, activatescaspases, and localizes intracellularly. CaThi combined with FLC, at concentrations thatalone do not inhibit F. solani, result in 100% death of F. solani when combined. Thedata presented in this study demonstrate that CaThi causes death of F. solani viaapoptosis; an intracellular target may also be involved. Combined treatment usingCaThi and FLC is a strong candidate for studies aimed at improved targeting of F.solani. This strategy is of particular interest because it minimizes selection of resistantmicroorganisms.