Investigação dos potenciais antibacteriano e citotóxico de compostos derivados do núcleo base [Fe-CYCLAM]

Abstract

The genus Staphylococcus makes up the microbiota of humans, animals and are one of the most successful colonizing pathogens, as they are among the leading causes of infections in healthcare and community settings. The resistance achieved by these microorganisms has emerged and spread globally, mainly by the methicillin-resistant Staphylococcus aureus (MRSA) species, posing a huge clinical and epidemiological challenge. The present study aimed to investigate the antibacterial and cytotoxic potentials of compounds derived from the base nucleus [Fe-Cyclam] in order to discover new actives capable of containing and controlling infections caused by S. aureus. Initially, in silico studies of the pharmacokinetic properties and biological targets of the cis-[Fe(cyclam)Cl2]Cl (D1), [Fe(cyclam)ox]PF6 (D2), trans-[Fe(cyclam)(acet)2]PF6 (D3) and [Fe(cyclam)salt]PF6 (D4) complexes were performed using online platforms (pkCSM® and Pass online®). The results were promising, demonstrating that the complexes meet acceptable criteria for possible classification as a new candidate drug and antibacterial agent. Next, cell viability was determined in peritoneal macrophages from BALB/c mice and J774A.1 cells exposed to the complexes (D1) to (D4). Only the complex (D3), at the concentration of 300 μg/mL, showed cytotoxicity to J774A.1. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against S. aureus strains ATCC® 25904™, S. aureus ATCC® 33591™ and the clinical isolate of S. aureus 05-0052, were determined. The complexes (D2) and (D4) showed MIC values of 50 μg/mL for all three S. aureus strains and the complexes (D1) and (D3) showed MIC values of 100 μg/mL for the same strains tested. The complexes (D2) and (D4) were selected for further tests, in order to elucidate the possible mechanisms of action. Through the cell density study it was possible to observe a reduction in the bacterial cell quantity for both (D2) and (D4). Mechanism of action studies were also performed for the complexes (D2) and (D4) in cell envelope by means of permeability with crystal violet, membrane leakage and metabolic activity and viability. The results showed that the complexes have an envelope action, interfering in the integrity of the cell membrane, leading to its inhibition. Furthermore, the action of inhibitory and subinhibitory concentrations of the complexes on the expression of virulence factors were evaluated. The results showed that the best action was on the enzyme catalase. Actions of complexes (D2) and (D4) on population biofilms were also evaluated by studying the adhesion and proliferation phases by spectrophotometry and scanning electron microscopy (SEM). In addition, it was investigated whether complexes (D2) and (D4) interfere with matrix composition. The analyses indicated a reduction in the adhesion and proliferation phases of the biofilms, however, this same reduction was not accompanied by the analysis of carbohydrates and proteins present in the matrix. The results presented provided an excellent perspective, indicating the complexes as a potential antibacterial therapy against infections caused by S. aureus.