Phylloseptin-1 is Leishmanicidal for Amastigotes of Leishmaniaamazonensis Inside Infected Macrophages.

Leishmania protozoans are the causal agents of neglected diseases that represent an important public health issue worldwide. The growing occurrence of drug-resistant strains of Leishmania and severe side effects of available treatments represent an important challenge for the leishmaniases treatment. We have previously reported the leishmanicidal activity of phylloseptin-1 (PSN-1), a peptide found in the skin secretion of Phyllomedusaazurea (=Pithecopus azureus), against Leishmaniaamazonensis promastigotes. However, its impact on the amastigote form of L. amazonensis and its impact on infected macrophages are unknown. In this work, we evaluated the effects of PSN-1 on amastigotes of L. amazonensis inside macrophages infected in vitro. We assessed the production of hydrogen peroxide and nitric oxide, as well as the levels of inflammatory and immunomodulatory markers (TGF-ß, TNF-α and IL-12), in infected and non-infected macrophages treated with PSN-1. Treatment with PSN-1 decreased the number of infected cells and the number of ingested amastigotes per cell when compared with the untreated cells. At 32 µM (64 µg/mL), PSN-1 reduced hydrogen peroxide levels in both infected and uninfected macrophages, whereas it had little effect on NO production or TGF-ß release. The effect of PSN-1 on IL-12 and TNF-α secretion depended on its concentration, but, in general, their levels tended to increase as PSN-1 concentration increased. Further in vitro and in vivo studies are needed to clarify the mechanisms of action of PSN-1 and its interaction with the immune system aiming to develop pharmacological applications.

Pravastatin modulates macrophage functions of Leishmania (L.) amazonensis-infected BALB/c mice.

The control of leishmaniases poses an important challenge due to the scarcity and toxicity of the pharmacological options available. We have previously shown that pravastatin significantly improves the course of the disease in Leishmania (L.) amazonensis-infected BALB/c mice. Since the drug caused no direct effect on the parasite, we decided to evaluate its immunomodulatory action in this experimental model. To evaluate the impact of pravastatin treatment, BALB/c mice infected or not with L. (L.) amazonensis were treated with pravastatin (20 mg/kg daily) or saline during 30 or 90 days and phagocytosis, hydrogen peroxide, nitric oxide and the tumor necrosis factor production by peritoneal macrophages were assessed. We showed that pravastatin increased the phagocytosis mediated by complement and immunoglobulin receptors (63.5 to 130.3; p=0.03, t test), but not that occurring via pattern recognition receptors, induced a rise of nitric oxide production by macrophages (2.1 µM to 12.9 µM; p=0.04, Mann-Whitney test), endowing these cells to better kill ingested leishmania organisms, caused no modification of the otherwise increased production of hydrogen peroxide by macrophages, and reduced the overproduction of tumor necrosis factor (166.6 pg/mL to 3.9 pg/mL; p=0.016, Mann-Whitney test), a major component of the exacerbated inflammation associated to leishmaniases. Our findings point to the potential usefulness of pravastatin as an adjunct to the treatment of leishmaniases, based on its powerful immunomodulatory effects and low toxicity.

Influence of long-term treatment with pravastatin on the survival, evolution of cutaneous lesion and weight of animals infected by Leishmania amazonensis.

The high toxicity of current drugs for treatment of leishmaniasis is a major hindrance for controlling the disease. Pravastatin is a well-known drug with anti-inflammatory and immunomodulatory properties that may modulate host defense mechanisms against Leishmania. We evaluated the influence of prolonged pravastatin treatment on the survival of Leishmania amazonensis-infected animals (BALB/c, C57BL6 mice and Syrian hamsters), including weekly measurement of cutaneous lesions (footpad thickness) and weight. Pravastatin improved survival of Leishmania-infected BALB/c mice but not of infected C57BL6 mice or hamsters. On the 50th week of follow-up, 71% of pravastatin-treated Leishmania-infected BALB/c mice were alive against 29% of control group (p<0.01). Low footpad thickness was found on BALB/c pravastatin treated mice from the 14th week (p<0.05), and 20th week onward for C57BL6 treated mice. Pravastatin treatment decreased weight loss in Leishmania-infected C57BL6 mice and Syrian hamsters, but not infected BALB/c mice. Our results points to beneficial effects of pravastatin on the evolution of the disease in the murine leishmaniasis model.