Antileishmanial activities of biosynthesized silver nanoparticles modulated by aqueous extract of Indigofera hetarantha Wall

Abstract

Background: Human visceral leishmaniasis (VL) is caused by Leishmania infantum, which causes severe problems if remains untreated. Macrophages are the primary cells that host the Leishmania parasites to complete their life cycle, however, sometimes it compromises the immune system and produces an exaggerated Th1 response that produces various effects. Both nitric oxide (NO) and reactive oxygen species (ROS) are important radicals that produce by macrophages to control L. infantum pathogenesis Methods & Materials: In this study, a simple, entirely green physical chemistry process was optimized for the biosynthesis of Ag nanoparticles (∼ 12.7 nm) using aqueous leaf extracts of Indigofera heterantha. The cytotoxicity in both macrophages (J774) and L. infantum promastigotes were assessed through MTT cell viability assay. Furthermore, we investigated the role of biogenic silver nanoparticles (AgNPs) induced NO and ROS in the control of L. infantum infection in in-vitro. The amount of nitrogen oxide(NO) (Griess method), and reactive oxygen species (ROS) (DCFDHA flouresecent method) in the nanoparticle activated macrophage cells after co-infection with L. infantum parasites. Results: An IC50 value was calculated as 49.41 ± 2.01 μg/ml and 16.72 ± 1.23 μg/ml against L. infantum promastigotes for extract and AgNPs respectively. Similarly, the non-toxicological concentration for macrophage cytotoxicity was greater than 100 μg/ml (extract) and 200 μg/ml (AgNPs). The infectivity index was calculated after 2, 24, and 48 hrs of infection. It was found that the infection index is decreasing with time. In addition the intracellular expression of free radical (NO & ROS) induced by AgNPs was evaluated in macrophage cells against L. infantum. We observed that macrophages produces a high amount of NO and ROS against the parasites. Conclusion: Therefore, we demonstrated that alone NO is not sufficient for the killing of L. infantum, whereas ROS also play a synergistic effect in the control of Leishmania parasites. Furthermore, it is concluded that biogenic silver nanoparticles modulated by aqueous extract of Teucrium stocksianum is a promising cost-effective and safer alternative for the development of antileishmanial drugs.