Epoxy-α-lapachone(2,2-Dimethyl-3,4-dihydro-spiro[2H-naphtho[2,3-b]pyran-10,2′-oxirane]-5(10H)-one): a promising molecule to control infections caused by protozoan parasites

ABSTRACT Natural products and their derivatives have been sources of search and research for new drugs for the treatment of neglected diseases. Naphthoquinones, a special group of quinones, are products of natural metabolites with a wide spectrum of biological activities and represent a group of interesting molecules for new therapeutic propositions. Among these compounds, lapachol stands out as a molecule from the heartwood of Tabebuia sp. whose structural changes resulted in compounds considered promising, such as epoxy-a-lapachone (ELAP). The biological activity of ELAP has been demonstrated, so far, for parasitic protozoa such as Leishmania spp., Trypanosoma cruzi and Plasmodium spp., species causing diseases needing new drug development and adequate health policy. This work gathers in vitro and in vivo studies on these parasites, as well as the toxicity profile, and the probable mechanisms of action elucidated until then. The potential of ELAP-based technology alternatives for a further drug is discussed here.

Antileishmanial Activity of 2-Methoxy-4H-spiro-[naphthalene-1,2'-oxiran]-4-one (Epoxymethoxy-lawsone): A Promising New Drug Candidate for Leishmaniasis Treatment.

Epoxymethoxylawsone is a naphthoquinone derivative promising as drug candidate for the treatment of leishmaniases. In the present work the effectiveness of epoxymethoxylawsone, and meglumine antimoniate on Leishmania (Leishmania) amazonensis parasites and on mice paw lesions of infected BALB/c mice was assessed. In an intracellular amastigotes assay, the half-maximal inhibitory concentration (IC50) value for epoxymethoxylawsone was slightly higher (1.7-fold) than that found for meglumine antimoniate. The efficacy of both drugs became more evident after 48 h of exposure when either the oxirane compound and reference drug reached 18-fold and 7.4-fold lower IC50 values (0.40 ± 0.001 µM and 0.60 ± 0.02 µM), respectively. Promastigotes were also affected by epoxymethoxylawsone after 24 h of incubation (IC50 = 45.45 ± 5.0 µM), but with IC50 6-fold higher than those found for intracellular amastigotes. Cytotoxicity analysis revealed that epoxymethoxylawsone (CC50 = 40.05 ± µM) has 1.7-fold higher effects than meglumine antimoniate (CC50 = 24.14 ± 2.6 µM). Treatment of the paw lesion in infected BALB/c mice with epoxymethoxy-lawsone led to a significant 27% reduction (p < 0.05) of the lesion size, for all administrated doses, compared to the control group. Lesion reduction was also detected after mice treatment with meglumine antimoniate, reaching 31.0% (0.23 mg of Sb(V)/Kg/day and 2.27 mg of Sb(V)/Kg/day) and 64.0% (22.7 mg of Sb(V)/Kg/day). In addition, mice lesion ultrastructural changes were evidenced in amastigotes. The set of data gathered here indicate that epoxymethoxylawsone has pronounced effects on parasites and merits furthering to the preclinical stage.

Understanding serine proteases implications on Leishmania spp lifecycle.

Serine proteases have significant functions over a broad range of relevant biological processes to the Leishmania spp lifecycle. Data gathered here present an update on the Leishmania spp serine proteases and the status of these enzymes as part of the parasite degradome. The serine protease genes (n = 26 to 28) in Leishmania spp, which encode proteins with a wide range of molecular masses (35 kDa-115 kDa), are described along with their degrees of chromosomal and allelic synteny. Amid 17 putative Leishmania spp serine proteases, only ∼18% were experimentally demonstrated, as: signal peptidases that remove the signal peptide from secretory pre-proteins, maturases of other proteins and with metacaspase-like activity. These enzymes include those of clans SB, SC and SF. Classical inhibitors of serine proteases are used as tools for the characterization and investigation of Leishmania spp. Endogenous serine protease inhibitors, which are ecotin-like, can act modulating host actions. However, crude or synthetic based-natural serine protease inhibitors, such as potato tuber extract, Stichodactyla helianthus protease inhibitor I, fukugetin and epoxy-α-lapachone act on parasitic serine proteases and are promising leishmanicidal agents. The functional interrelationship between serine proteases and other Leishmania spp proteins demonstrate essential functions of these enzymes in parasite physiology and therefore their value as targets for leishmaniasis treatment.

Nova proposta para o tratamento da Leishmaniose tegumentar usando antimoniato de meglumina e oxiranos em associação / New proposal for the treatment of cutaneous leishmaniasis using meglumine antimoniate and oxirans in combination

Esta tese porpõe uma nova abordagem para o tratamento da leishmaniose tegumentar com o antimoniato de N-metilglucamina (antimoniato de meglumina - AM) associado a dois derivados oxiranos. O estudo foi conduzido em modelo murino de infecção in vitro e in vivo por Leishmania (Leishmania) amazonensis. Na primeira etapa do estudo foram descritas alterações histológicas causadas por epoxi-α-lapachona, epoximetil-lausona e AM em camundongos BALB/c não infectados, bem como a predição de algumas de suas propriedades farmacocinéticas. Os resultados indicaram que tanto os oxiranos quanto o antimoniato de meglumina induzem alterações histopatológicas nos órgãos analisados. O epoximetil-lausona foi o mais tóxico para o tecido pulmonar, enquanto os danos mais graves no coração foram causados pelo epoxi-α-lapachona. O AM causou alterações leves a moderadas nos tecidos cardíacos e pulmonares, mas sem qualquer efeito detectado nos tecidos cerebrais. Na segunda etapa foi necessário avaliar a eficácia do epoximetil-lausona sobre a infecção de macrófagos e camundongos BALB/c infectados por L.(L.) amazonensis. Em amastigotas intracelulares, o IC50 do epoximetil-lausona foi ligeiramente superior ao do AM (7,41 ± 0,2 e 4,43 ± 0,25 µM, respectivamente), sendo o efeito mais evidente após 48 horas de exposição (18 vezes e 7,4 vezes inferiores, respectivamente).

Os promastigotas também foram afetados pelo composto, porém o IC50 foi seis vezes maior (45,45 ± 5,0µM), indicando sua especificidade sobre os amastigotas intracelulares. A análise de citotoxicidade revelou que o epoximetil-lausona tem um efeito menor (1,7 ×) comparado ao AM (40,05 ± 3,0 e 24,14 ± 2,6 µM). O tratamento com três doses do epoximetil-lausona reduziu a lesão da pata dos animais infectados em 27 %, enquanto a redução obtida com o AM chegou a 31% nas doses baixa e intermediária, e 64% com a dose mais alta, comparado ao grupo controle. Alterações ultraestruturais detectadas nos amastigotas da lesão constataram comprometimento da integridade dos parasitos. Na etapa final deste estudo foi demonstrado o efeito do tratamento com o AM associado aos oxiranos epoxi-α-lapachona e epoximetil-lausona sobre a infecção experimental in vitro e in vivo. Os compostos foram testados individualmente e em combinações, seguindo as razões: 3:1; 1:1 e 1:3 (p/v) sobre macrófagos infectados. Todos os compostos, assim como suas combinações mostraram índices endocíticos muito inferiores ao grupo controle, sendo as maiores reduções obtidas nas razões de 3:1. O tratamento de camundongos BALB/c com os compostos individualmente e combinados nas mesmas razões levou a reduções significativas das lesões. O melhor efeito das combinações foi observado nas razões de 3:1. Os resultados indicaram que a associação do AM com os oxiranos produz um incremento no efeito leishmanicida, e pode ser considerada uma nova abordagem para o tratamento da leishmaniose cutânea. (AU)

Evidence for Tissue Toxicity in BALB/c Exposed to a Long-Term Treatment with Oxiranes Compared to Meglumine Antimoniate.

Leishmaniasis remains a serious public health problem in developing countries without effective control, whether by vaccination or chemotherapy. Part of the failure of leishmaniasis control is due to the lack of new less toxic and more effective drugs able to eliminate both the lesions and the parasite. Oxiranes derived from naphthoquinones now being assayed are promising drugs for the treatment of this group of diseases. The predicted pharmacokinetic properties and toxicological profiles of epoxy-α-lapachone and epoxymethoxy-lawsone have now been compared to those of meglumine antimoniate, and histological changes induced by these drugs in noninfected BALB/c mice tissues are described. Effects of these compounds on liver, kidney, lung, heart, and cerebral tissues of healthy mice were examined. The data presented show that both these oxiranes and meglumine antimoniate induce changes in all BALB/c mice tissues, with the lung, heart, and brain being the most affected. Epoxymethoxy-lawsone was the most toxic to lung tissue, while most severe damage was caused in the heart by epoxy-α-lapachone. Meglumine antimoniate caused mild-to-moderate changes in heart and lung tissues.

Epoxy-α-lapachone has in vitro and in vivo anti-leishmania (Leishmania) amazonensis effects and inhibits serine proteinase activity in this parasite.

Leishmania (Leishmania) amazonensis is a protozoan that causes infections with a broad spectrum of clinical manifestations. The currently available chemotherapeutic treatments present many problems, such as several adverse side effects and the development of resistant strains. Natural compounds have been investigated as potential antileishmanial agents, and the effects of epoxy-α-lapachone on L. (L.) amazonensis were analyzed in the present study. This compound was able to cause measurable effects on promastigote and amastigote forms of the parasite, affecting plasma membrane organization and leading to death after 3 h of exposure. This compound also had an effect in experimentally infected BALB/c mice, causing reductions in paw lesions 6 weeks after treatment with 0.44 mM epoxy-α-lapachone (mean lesion area, 24.9 ± 2.0 mm(2)), compared to untreated animals (mean lesion area, 30.8 ± 2.6 mm(2)) or animals treated with Glucantime (mean lesion area, 28.3 ± 1.5 mm(2)). In addition, the effects of this compound on the serine proteinase activities of the parasite were evaluated. Serine proteinase-enriched fractions were extracted from both promastigotes and amastigotes and were shown to act on specific serine proteinase substrates and to be sensitive to classic serine proteinase inhibitors (phenylmethylsulfonyl fluoride, aprotinin, and antipain). These fractions were also affected by epoxy-α-lapachone. Furthermore, in silico simulations indicated that epoxy-α-lapachone can bind to oligopeptidase B (OPB) of L. (L.) amazonensis, a serine proteinase, in a manner similar to that of antipain, interacting with an S1 binding site. This evidence suggests that OPB may be a potential target for epoxy-α-lapachone and, as such, may be related to the compound's effects on the parasite.