Atividade antimicobacteriana, citotoxicidade e interaÃÃo com macrÃfagos J774 de lipossomas contendo Ãcido Ãsnico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Secondary lichen metabolite usnic acid (UA) [2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzofurano] is known by its antimicrobial activity against gram-positive bacteria and mycobacteria. Pulmonary tuberculosis is characterized by involvement of macrophages containing inside a large number of Mycobacterium tuberculosis. Liposomes have long been recognized as good carriers in targeting of drugs to cells. There is a need for new compounds to treat mycobacterial infections because no new antibiotic have been developed since the 1970s. In this framework, the aim of this study was to assess the in vitro antimicrobial activity of UA-loaded liposomes against M. tuberculosis and to investigate their interactions with macrophages. Liposomes were prepared using the hydration lipid film technique with subsequent sonication. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against M. tuberculosis H37Rv were determined according to the microdilution Alamar blue assay. The cytotoxicity of UA was evaluated on J774 macrophages and the cell viability was detected by the standard MTT assay. The cellular uptake studies were carried out on J774 macrophages using fluorescence spectroscopy. The values of MIC and MBC for free UA were 6.5 and 32 μg/ml, respectively. In contrast, UA-loaded liposomes exhibited a MIC of 5.85 μg/ml and a MBC of 16 μg/ml. The concentration required to inhibit 50% of cell proliferation (IC50) were 22.5 and 12.5 μg/ml for free and encapsulated UA, respectively. The cytotoxic effect of UA-loaded liposomes on J774 macrophages was thus two-fold higher than free UA. An enhancement in the intracellular uptake of UA-loaded liposomes was verified by the highest detected fluorescence emission (21.57 x 104 c.p.s) in comparison with free UA (9.54 x 104 c.p.s). Besides, the liposomal formulation provided an almost invariable amount of UA inside macrophages during a long time (30 h, p <0.05). These results indicated that a strongly interaction exists between liposomes and J774 macrophages, facilitating UA penetration into cells and thereby remarkably improving its activity against the M. tuberculosis

ASSUNTO(S)

usnic acid farmacia citotoxicidade cytotoxicity interaÃÃo celular Ãcido Ãsnico lipossomas antimycobacterial activity cellular uptake atividade antimicobacteriana liposomes

ACESSO AO ARTIGO

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