Silver(I) and Copper(II) Complexes of 1,10-Phenanthroline-5,6-Dione Against Phialophora verrucosa: A Focus on the Interaction With Human Macrophages and Galleria mellonella Larvae.

Marcela Q Granato,Thabatta L S A Rosa,Michael Devereux,Malachy Mccann,Renata S Nascimento,Maria C V Pessolani,Marcos D Pereira,Lucimar F Kneipp,Marta H Branquinha,André L S Santos,Thaís P Mello

doi:10.3389/fmicb.2021.641258

Abstract

Phialophora verrucosa is a dematiaceous fungus that causes mainly chromoblastomycosis, but also disseminated infections such as phaeohyphomycosis and mycetoma. These diseases are extremely hard to treat and often refractory to current antifungal therapies. In this work, we have evaluated the effect of 1,10-phenanthroline-5,6-dione (phendione) and its metal-based complexes, [Ag (phendione)2]ClO4 and [Cu(phendione)3](ClO4)2.4H2O, against P. verrucosa, focusing on (i) conidial viability when combined with amphotericin B (AmB); (ii) biofilm formation and disarticulation events; (iii) in vitro interaction with human macrophages; and (iv) in vivo infection of Galleria mellonella larvae. The combination of AmB with each of the test compounds promoted the additive inhibition of P. verrucosa growth, as judged by the checkerboard assay. During the biofilm formation process over polystyrene surface, sub-minimum inhibitory concentrations (MIC) of phendione and its silver(I) and copper(II) complexes were able to reduce biomass and extracellular matrix production. Moreover, a mature biofilm treated with high concentrations of the test compounds diminished biofilm viability in a concentration-dependent manner. Pre-treatment of conidial cells with the test compounds did not alter the percentage of infected THP-1 macrophages; however, [Ag(phendione)2]ClO4 caused a significant reduction in the number of intracellular fungal cells compared to the untreated system. In addition, the killing process was significantly enhanced by post-treatment of infected macrophages with the test compounds. P. verrucosa induced a typically cell density-dependent effect on G. mellonella larvae death after 7 days of infection. Interestingly, exposure to the silver(I) complex protected the larvae from P. verrucosa infection. Collectively, the results corroborate the promising therapeutic potential of phendione-based drugs against fungal infections, including those caused by P. verrucosa.

Highlights

Phialophora verrucosa is a well-known chromoblastomycosis etiological agent that may cause other cutaneous and subcutaneous diseases as well as disseminated infections, such as phaeohyphomycosis and mycetoma (Turiansky et al, 1995; Tong et al, 2013; Queiroz-Telles et al, 2017)
The present study was designed to investigate the effects of phendione, [Ag(phendione)2]+, and [Cu(phendione)3]2+ on P. verrucosa, focusing on (i) the combination of these test agents with the classical antifungal drug, amphotericin B, (ii) biofilm formation and disarticulation, (iii) the in vitro interaction with human macrophages; and (iv) in vivo infection using G. mellonella larvae as a model
Macrophages infected with either untreated or treated conidial cells were lysed with sterile cold water, and the suspensions were plated onto Sabouraud dextrose agar (SDA) medium to count the number of colony forming units (CFU; Palmeira et al, 2008)

Summary

INTRODUCTION

Phialophora verrucosa is a well-known chromoblastomycosis etiological agent that may cause other cutaneous and subcutaneous diseases as well as disseminated infections, such as phaeohyphomycosis and mycetoma (Turiansky et al, 1995; Tong et al, 2013; Queiroz-Telles et al, 2017). Several studies have highlighted the biofilm relevance in the fungal pathogenesis, contextualizing the real issue of this structure formation in the medical settings (Vila and Rozental, 2016; Santos et al, 2018; Wall et al, 2019) This complex microbial community, which is adhered to a surface, is surrounded by an extracellular matrix that gives its cells several advantages, such as increased virulence, immune system, and environmental stress protection as well as resistance to antimicrobial agents (Costa-Orlandi et al, 2017; Santos et al, 2018). The present study was designed to investigate the effects of phendione, [Ag(phendione)2]+, and [Cu(phendione)3]2+ on P. verrucosa, focusing on (i) the combination of these test agents with the classical antifungal drug, amphotericin B, (ii) biofilm formation and disarticulation, (iii) the in vitro interaction with human macrophages; and (iv) in vivo infection using G. mellonella larvae as a model

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT