Decoding the anti-Leishmania braziliensis activity of 1,10-phenanthroline-5,6-dione and its silver- and copper-based complexes: In vitro and in vivo approaches

• Published in: European journal of medicinal chemistry reports 2022-12, Vol.6, p.100093, Article 100093
• Main Authors: Santos, André L.S., Lima, Ana Karina C., Oliveira, Simone S.C., dos Santos, Rosiane F., Devereux, Michael, McCann, Malachy, Branquinha, Marta H., Dutra, Patrícia M.L.
• Format: Article
• Language: English
• Subjects: 1,10-Phenanthroline-5,6-dione; Chemotherapy; Coordination complexes; Infection; Leishmania; Virulence
• ISSN: 2772-4174; 2772-4174
• DOI: 10.1016/j.ejmcr.2022.100093

Leishmaniasis is a neglected tropical disease, whose chemotherapy still presents a series of severe side effects for the patient. Recently, our group published the leishmanicidal action of 1,10-phenanthroline (1), 1,10-phenanthroline-5,6-dione (phendione, 2) and its silver(I) [Ag(phendione)2]ClO4 (3) and copper(II) [Cu(phendione)3](ClO4)2.4H2O (4) complexes against Leishmania braziliensis. Herein, we deciphered the mechanisms of anti-L. braziliensis action of these promising compounds. The IC50 values were calculated for L. braziliensis promastigotes and the potency order was: 4 (0.5 ​μM) ​> ​3 (6.1 ​μM) ​> ​2 (21.3 ​μM) ​> ​1 (32.7 ​μM). Treatment of promastigotes with test compounds induced mitochondrial dysfunction with concomitant increment in the production of intracellular reactive oxygen species, culminating in parasite death by apoptosis as judged by the increased percentage of annexin-positive/propidium iodide-negative parasites and DNA cleavage (classical phenotypic markers of apoptotic cells). Subsequently, the effects of these test compounds on in vitro interaction between L. braziliensis and hamster macrophages showed a significant reduction in the number of intracellular amastigotes, and consequently parasite death by apoptosis. The test compounds presented a protective action in in vivo hamster infections without presenting toxicity to the mammalian host. The compounds limited the development of the paw lesion in hamsters infected with L. braziliensis as well as drastically reducing the number of parasites in both infected paw and lymph nodes draining the lesion, with 4 being the most effective compound. Collectively, our results emphasize the high potential of metal-based compounds, particularly 4, as new, safe and effective alternatives for the treatment of L. braziliensis infection. [Display omitted] •Phendione and its metal complexes, Ag-phendione and Cu-phendione affected the viability of Leishmania braziliensis.•Ag-phendione and Cu-phendione promoted the expression of apoptotic markers.•Test complexes were not toxic to mammalian host (hamster).•Test complexes reduced the in vitro interaction between L. braziliensis and hamster macrophages.•Test complexes presented a protective action in in vivo hamster infections.