Phylloseptin-1 is Leishmanicidal for Amastigotes ofLeishmania amazonensisInside 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 ofLeishmaniaand 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 ofPhyllomedusaazurea(=Pithecopus azureus), againstLeishmaniaamazonensispromastigotes. However, its impact on the amastigote form ofL. amazonensisand its impact on infected macrophages are unknown. In this work, we evaluated the effects of PSN-1 on amastigotes ofL. amazonensisinside 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-beta, TNF-alpha 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 mu M (64 mu g/mL), PSN-1 reduced hydrogen peroxide levels in both infected and uninfected macrophages, whereas it had little effect on NO production or TGF-beta release. The effect of PSN-1 on IL-12 and TNF-alpha 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.