Study of the biological profile of the tris-(1,10-phenanthroline)iron(II) complex and mechanisms of action against Mycobacterium tuberculosis

Author(s)

Mariana Cristina Solcia

• Document type: Master's Dissertation
• Press: Araraquara. 2020-08-18.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Farmacêuticas. Araraquara
• Defense date: 2018-10-18
• Advisor: Fernando Rogerio Pavan

Abstract

Tuberculosis (TB) is considered a prevalent epidemic and according to the World Health Organization (WHO) is the deadliest transmissible disease in the world. The emergence of resistance to the major classes of antimicrobial agents and the estimation that around 2 billion people have the microorganism latent throughout the world are factors that constitute a serious threat to public health and contribute directly to the incidence of the disease. The need to develop new active agents to combat TB poses a major challenge for the control and treatment of TB. In this work, the reuse strategy of the tris-(1,10-phenanthroline)iron(II) complex, ([Fe(phen)3]2+), was explored, since it has the ability to disturb the functioning of a large variety of biological systems besides being easy to obtain and low cost. The objective was to search for new applications of this molecule, investigating its potential and possible mechanisms of action against Mycobacterium tuberculosis, the main agent causing TB. The activity of ([Fe(phen)3]2+) against M. tuberculosis strains was determined by the plaque microdilution method (REMA), where the complex showed satisfactory inhibition of sensitive bacilli under normal conditions, without losing its activity when submitted to different culture medium conditions; showed inhibition of latent bacteria by the LORA method and effectively inhibited strains with multiple resistance profiles (MDR-TB) and extensive (XDR-TB) profiles. In intramacrophagic assays, ([Fe(phen)3]2+) was able to eliminate more than 80% of the mycobacteria contained within macrophages, a profile comparable to the drug rifampicin, the first-line treatment for TB. The complex exhibits an excellent selectivity index, demonstrated in cytotoxicity and narrow activity spectra, as it does not present inhibition against other pathogens tested. In animal plasma assays after single oral dose application in BALB/c mice, it has been shown to be bioavailable from 2h after administration. In order to investigate the possible mechanism of action, the mycobacteriophage assay indicated a strong relationship of the complex in inhibiting bacterial protein synthesis. The ability of the complex to inhibit cell wall synthesis by the thin layer chromatography technique and possible inhibition of efflux pumps was also investigated by the ethidium bromide accumulation assay, in which the complex showed no activity. In addition to these assays in order to unravel the target(s) of ([Fe(phen)3]2+), the isolation of complex resistant bacteria was carried out in order to further investigate a possible mutant through genomic sequencing searching for the target of mutations present and relate to the target site of the complex in mycobacteria. It was also determined that M. tuberculosis presents a low frequency of mutations to the complex. With the results obtained, ([Fe(phen)3]2+) shows to be very promising in the studies, since it presents activities in different forms of the disease, as latent and intracellularly in macrophages. In addition, it is active in antimicrobial resistant bacteria that exist in the treatment of TB, thus complying with the WHO declaration to prioritize research and development aimed at M. tuberculosis, mainly due to resistance indexes. (AU)

• FAPESP's process: 16/24633-0 - Study of the biological profile of tris-(1,10-phenanthroline) iron (II) complex and possible mechanisms of action against Mycobacterium tuberculosis
• Grantee: Mariana Cristina Solcia
• Support Opportunities: Scholarships in Brazil - Master