Leishmania is a digenetic protozoan parasite causing leishmaniasis in humans. The different clinical forms of leishmaniasis are caused by more than twenty species of Leishmania that are transmitted by nearly thirty species of phlebotomine sand flies. Pentavalent antimonials (such as Pentostam or Glucantime) are the first line drugs for treating leishmaniasis. Recent studies suggest that pentavalent antimony (Sb(V)) acts as a pro-drug, which is converted to the more active trivalent form (Sb(III)). However, sensitivity to trivalent antimony varies among different Leishmania species. In general, Leishmania species causing cutaneous leishmaniasis (CL) are more sensitive to Sb(III) than the species responsible for visceral leishmaniasis (VL). Leishmania aquaglyceroporin (AQP1) facilitates the adventitious passage of antimonite down a concentration gradient. In this study, we show that Leishmania species causing CL accumulate more antimonite, and therefore exhibit higher sensitivity to antimonials, than the species responsible for VL. This species-specific differential sensitivity to antimonite is directly proportional to the expression levels of AQP1 mRNA. We show that the stability of AQP1 mRNA in different Leishmania species is regulated by their respective 3’-untranslated regions. The differential regulation of AQP1 mRNA explains the distinct antimonial sensitivity of each species.
The efficacy of two mesoionic derivatives (MI-H-H and MI-4-OCH 3 ) was evaluated in CBA/J mice infected with Leishmania amazonensis. Treatment with these compounds demonstrated that the MI-4-OCH 3 derivative and the reference drug meglumine antimoniate (Glucantime) presented significant activity relative to an untreated control. No apparent hepatic or renal toxicity due to these mesoionic compounds was found.
methylene]-1H-pyrazole-4-carbohydrazides. -(BERNARDINO, A. M. R.; GOMES, A. O.; CHARRET, K. S.; FREITAS, A. C. C.; MACHADO, G. M. C.; CANTO-CAVALHEIRO, M. M.; LEON, L. L.; AMARAL*, V. F.; Eur.
Newly synthesized pyrazole carbohydrazide derivatives with substituents X = Br/Y = NO(2) and X = NO(2)/Y = Cl were independently investigated in the CBA mouse model of cutaneous leishmaniasis. Animals were infected with Leishmania amazonensis and treated two weeks after the parasitic infection with the pyrazole carbohydrazides for 45 days. Oral treatment with both compounds controlled evolution of footpad cutaneous lesions and dissemination of parasites to draining lymph nodes. Nitric oxide generation was observed in supernatants of lymph node cells from infected CBA mice that were treated with these compounds. The pyrazole carbohydrazide derivatives did not show any toxicity or cause alterations in body weight, plasma concentrations of alanine aminotransferase and aspartate aminotransferase, and urinary creatinine levels, but promoted a small decrease in blood neutrophils. These results provide new perspectives on the development of drugs with activities against leishmaniasis.
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