Low doses of 3-phenyl-lawsone or meglumine antimoniate delivery by tattooing route are successful in reducing parasite load in cutaneous lesions of Leishmania (Viannia) braziliensis-infected hamsters.

Current therapeutic ways adopted for the treatment of leishmaniasis are toxic and expensive including parasite resistance is a growing problem. Given this scenario, it is urgent to explore treatment alternatives for leishmaniasis. The aim of this study was to evaluate the effect of 3-phenyl-lawsone (3-PL) naphthoquinone on Leishmania (Viannia) braziliensis infection, both in vitro and in vivo, using two local routes of administration: subcutaneous (higher dose) and tattoo (lower dose). In vitro 3-PL showed low toxicity for macrophages (CC50 >3200 µM/48h) and activity against intracellular amastigotes (IC50 = 193 ± 19 µM/48h) and promastigotes (IC50 = 116 ± 26 µM/72h), in which induced increased ROS generation. Additionally, 3-PL up-regulated the production of cytokines such as tumor necrosis factor alpha (TNF-α), monocyte chemotactic protein 1 (MCP-1), interleukin-6 (IL-6) and IL-10 in infected macrophages. However, the anti-amastigote action was independent of nitric oxide production. Treatment of hamsters infected with L. (V.) braziliensis from one week after infection with 3-PL by subcutaneous (25 µg/Kg) or tattooing (2.5 µg/Kg) route, during 3 weeks (3 times/week) or 2 weeks (2 times/week) significantly decreased the parasite load (p<0.001) in the lesion. The reduction of parasite load by 3-PL treatment was comparable to reference drug meglumine antimoniate administered by the same routes (subcutaneous 1mg/Kg and tattoo 0.1mg/Kg). In addition, treatment started from five weeks after infection with 3-PL per tattoo also decreased the parasite load. These results show the anti-leishmanial effect of 3-PL against L. (V.) braziliensis and its efficacy by subcutaneous (higher dose) and tattoo (lower dose) routes. In addition, this study shows that drug delivery by tattooing the lesion allows the use of lower doses than the conventional subcutaneous route, which may support the development of a new therapeutic strategy that can be adopted for leishmaniasis.

Therapeutic effect of oral quercetin in hamsters infected with Leishmania Viannia braziliensis.

Leishmaniasis is a parasitic disease caused by several species of intracellular protozoa of the genus Leishmania that present manifestations ranging from cutaneous ulcers to the fatal visceral form. Leishmania Viannia braziliensis is an important species associated with American tegumentary leishmaniasis and the main agent in Brazil, with variable sensitivity to available drugs. The search for new therapeutic alternatives to treat leishmaniasis is an urgent need, especially for endemic countries. Not only is quercetin well known for its antioxidant activity in radical scavenging but also several other biological effects are described, including anti-inflammatory, antimicrobial, and pro-oxidant activities. This study aimed to investigate the flavonoid quercetin's therapeutic potential in L. (V.) braziliensis infection. Quercetin showed antiamastigote (IC50 of 21 ± 2.5 µM) and antipromastigote (25 ± 0.7 µM) activities and a selectivity index of 22. The treatment of uninfected or L. (V.) braziliensis-infected macrophages with quercetin increased reactive oxygen species (ROS)/H202 generation without altering Nitric Oxide (NO) production. Oral treatment with quercetin of infected hamsters, starting at 1 week of infection for 8 weeks, reduced the lesion thickness (p > 0.01) and parasite load (p > 0.001). The results of this study suggest that the antiamastigote activity of the flavonoid quercetin in vitro is associated, at least in part, with the modulation of ROS production by macrophages. The efficacy of oral quercetin treatment in hamsters infected with L. (V.) braziliensis was presented for the first time and shows its promising therapeutic potential.

Efficacy of Spironolactone Treatment in Murine Models of Cutaneous and Visceral Leishmaniasis.

Translational studies involving the reuse and association of drugs are approaches that can result in higher success rates in the discovery and development of drugs for serious public health problems, including leishmaniasis. If we consider the number of pathogenic species in relation to therapeutic options, this arsenal is still small, and each drug possesses a disadvantage in terms of toxicity, efficacy, price, or treatment regimen. In the search for new drugs, we performed a drug screening of L. amazonensis promastigotes and intracellular amastigotes of fifty available drugs belonging to several classes according to their pharmacophoric group. Spironolactone, a potassium-sparing diuretic, proved to be the most promising drug candidate. After demonstrating the in vitro antileishmanial activity, we evaluated the efficacy on a murine experimental model with L. amazonensis and L. infantum. The treatment controlled the cutaneous lesion and reduced the parasite burden of L. amazonensis significantly, as effectively as meglumine antimoniate. The treatment of experimental visceral leishmaniasis was effective in reducing the parasite load on the main affected organs (spleen and liver) via high doses of spironolactone. The association between spironolactone and meglumine antimoniate promoted better control of the parasite load in the spleen and liver compared to the group treated with meglumine antimoniate alone. These results reveal a possible benefit of the concomitant use of spironolactone and meglumine antimoniate that should be studied more in depth for the future possibility of repositioning for leishmaniasis co-therapy.

Leishmania amazonensis: Increase in ecto-ATPase activity and parasite burden of vinblastine-resistant protozoa.

Leishmania amazonensis is a protozoan parasite that induces mucocutaneous and diffuse cutaneous lesions upon infection. An important component in treatment failure is the emergence of drug-resistant parasites. It is necessary to clarify the mechanism of resistance that occurs in these parasites to develop effective drugs for leishmaniasis treatment. Promastigote forms of L. amazonensis were selected by gradually increasing concentrations of vinblastine and were maintained under continuous drug pressure (resistant cells). Vinblastine-resistant L. amazonensis proliferated similarly to control parasites. However, resistant cells showed changes in the cell shape, irregular flagella and a decrease in rhodamine 123 accumulation, which are factors associated with the development of resistance, suggesting the MDR phenotype. The Mg-dependent-ecto-ATPase, an enzyme located on cell surface of Leishmania parasites, is involved in the acquisition of purine and participates in the adhesion and infectivity process. We compared control and resistant L. amazonensis ecto-enzymatic activities. The control and resistant Leishmania ecto-ATPase activities were 16.0 ± 1.5 nmol Pi × h(-1) × 10(-7) cells and 40.0 ± 4.4 nmol Pi × h(-1) × 10(-7)cells, respectively. Interestingly, the activity of other ecto-enzymes present on the L. amazonensis cell surface, the ecto-5' and 3'-nucleotidases and ecto-phosphatase, did not increase. The level of ecto-ATPase modulation is related to the degree of resistance of the cell. Cells resistant to 10 µM and 60 µM of vinblastine have ecto-ATPase activities of 22.7 ± 0.4 nmol Pi × h(-1) × 10(-7) cells and 33.8 ± 0.8 nmol Pi × h(-1) × 10(-7)cells, respectively. In vivo experiments showed that both lesion size and parasite burden in mice infected with resistant parasites are greater than those of L. amazonensis control cells. Furthermore, our data established a relationship between the increase in ecto-ATPase activity and greater infectivity and severity of the disease caused by vinblastine-resistant L. amazonensis promastigotes. Taken together, these data suggest that ecto-enzymes could be potential therapeutic targets in the struggle against the spread of leishmaniasis, a neglected world-wide public health problem.