The Effect of Ursolic Acid on Leishmania (Leishmania) amazonensis Is Related to Programed Cell Death and Presents Therapeutic Potential in Experimental Cutaneous Leishmaniasis

Abstract

Among neglected tropical diseases, leishmaniasis is one of the most important ones, affecting more than 12 million people worldwide. The available treatments are not well tolerated, and present diverse side effects, justifying the search for new therapeutic compounds. In the present study, the activity of ursolic acid (UA) and oleanolic acid (OA) were assayed in experimental cutaneous leishmaniasis (in vitro and in vivo). Promastigote forms of L. amazonensis were incubated with OA and UA for 24h, and effective concentration 50% (EC50) was estimated. Ultraestructural alterations in Leishmania amazonensis promastigotes after UA treatment were evaluated by transmission electron microscopy, and the possible mode of action was assayed through Annexin V and propidium iodide staining, caspase 3/7 activity, DNA fragmentation and transmembrane mitochondrial potential. The UA potential was evaluated in intracellular amastigotes, and its therapeutic potential was evaluated in L. amazonensis infected BALB/c mice. UA eliminated L. amazonensis promastigotes with an EC50 of 6.4 μg/mL, comparable with miltefosine, while OA presented only a marginal effect on promastigote forms at 100 μg/mL. The possible mechanism by which promastigotes were eliminated by UA was programmed cell death, independent of caspase 3/7, but it was highly dependent on mitochondria activity. UA was not toxic for peritoneal macrophages from BALB/c mice, and it was able to eliminate intracellular amastigotes, associated with nitric oxide (NO) production. OA did not eliminate amastigotes nor trigger NO. L. amazonensis infected BALB/c mice submitted to UA treatment presented lesser lesion size and parasitism compared to control. This study showed, for the first time, that UA eliminate promastigote forms through a mechanism associated with programed cell death, and importantly, was effective in vivo. Therefore, UA can be considered an interesting candidate for future tests as a prototype drug for the treatment of cutaneous leishmaniasis.

Therapeutic effect of ursolic acid in experimental visceral leishmaniasis

“…Furthermore, UA was confirmed to possess antiprotozoal activities. Similarly to its effect on tumor cells, this triterpene induced programmed cell death in L. (L.) amazonensis , and presented therapeutic efficacy in the model of American Tegumentar Leishmaniasis (Yamamoto et al., 2015). …”

“…Although the leishmanicidal action of UA ( in vitro ) was already evaluated (Passero et al., 2011, Yamamoto et al., 2015), its action in experimental models of leishmaniasis was poorly demonstrated until now. In this regard, Yamamoto and collaborators (Yamamoto et al., 2014) showed that UA treatment of L. (L.) amazonensis- infected BALB/c mice decreased skin parasitism, which was associated with the preservation of the epidermis and dermis as a possible consequence of IFN-γ production.…”

“…(Gnoatto et al., 2008, Bero et al., 2011, Begum et al., 2014). Recently, it was demonstrated that ursolic acid (UA) displayed activity against promastigote and amastigote forms of L. (L.) amazonensis , L. (V.) braziliensis , L. (L.) chagasi , and L. (L.) major (Passero et al., 2011, Begum et al., 2014, Yamamoto et al., 2014, Yamamoto et al., 2015), suggesting that UA presents multispectral action. In spite of that, few works have performed in vivo studies in order to evaluate the therapeutic potential of this triterpene and, more importantly, up to now there has not been any report analyzing the therapeutic action of this compound on VL, one of the most important medical conditions caused by Leishmania parasites.…”

Antileishmanial Activity and Immunomodulatory Effects of Tricin Isolated from Leaves of Casearia arborea (Salicaceae)

“…Nitric oxide (NO) production by host macrophages has been considering one of the key weapons used for the antimicrobial defense against intracellular pathogens, including Leishmania parasites . Many plant‐derived compounds have been described to increase NO production in macrophage as a Leishmania killing mechanism . Therefore, the present work suggests that tricin ( 1 ) modulated the respiratory burst of macrophage to a leishmanicidal state, possibly contributing to the parasite elimination.…”

Two CYP716A subfamily cytochrome P450 monooxygenases of sweet basil play similar but nonredundant roles in ursane‐ and oleanane‐type pentacyclic triterpene biosynthesis

“…Moreover, these PCTs might be involved in maintaining the mechanical strength of the cuticular matrix by functioning as nanofillers (Tsubaki et al, 2013). Ursolic acid and oleanolic acid exhibit a wide spectrum of pharmacological activities, including anti-carcinogenic, hepatoprotective, antiinflammatory, anti-oxidant and anti-microbial properties, and products based on these PCTs are available in global markets as dietary supplements, over-the-counter drugs and cosmetics (Kunkel et al, 2011;Pollier & Goossens, 2012;Wo zniak et al, 2015;Yamamoto et al, 2015;Kashyap et al, 2016;Silva et al, 2016). Moreover, oleanolic acid derivatives (bardoxolone methyl and omaveloxolone) are currently undergoing advanced clinical studies for the treatment of pulmonary hypertension, chronic kidney disease, Friedreich's ataxia, mitochondrial myopathies and melanoma patients, and for the prevention of corneal endothelial cell loss in cataract surgery patients (http://reatapharma.com/).…”