Fig. 7

Cell behavior after treatment with AgNP-PVP-MA nanocomposite. After infection of macrophages with Leishmania amazonensis and later treatment with the AgNP-PVP-MA, generated that, as mechanism of action promoted by nanocomposite, the pro-inflammatory and anti-inflammatory cytokines TNF-α, IL-4, and IL-17 A and the chemokine MIP-1α were expressed, as the main mediators during infection of the parasite this study; being involved in different roles as resistance, susceptibility and immunopathogenesis, and being indispensable during infection control of parasite in the leishmaniasis. Resistance to leishmaniasis is related to the development at a Th1 response and its respective production of pro-inflammatory cytokines, like TNF-α, IL-6, and, IL-17 A, which are responsible for activating macrophages and generating the death of parasites by the production of NO and ROS, responsible for the elimination of intracellular amastigotes. Our results may indicate that the ROS and NO pathways are not stimulated by the nanocomposite, since their expression was low in ROS and NO, which leads to a low activation and stress of macrophages in the presence of the nanocomposite, can being other pathways can being involved in the action mechanism these. On the other hand, less IL-4 and IL-17 A were produced and IL-17 was reduced in the presence of the nanocomposite. In addition, the chemokine MIP-1α produced in large quantities by macrophages in our study is characterized by chemotactic and pro-inflammatory effects and is crucial for immune responses toward infection and inflammation. Furthermore, neutrophils, eosinophils and basophils, are favored by the presence of TNF-α, responsible for pro-inflammatory functions as well as the death of parasites because of their cytotoxic function. They also induce the synthesis and release of other pro-inflammatory cytokines by macrophages. Parasite death was determined by the presence of ultrastructural changes in the two developmental forms of the Leishmania, which were highlighted in the promastigote form as a compromised nucleus, possible initiation of the apoptotic process and chromatin condensation in the nuclear periphery and the presence of a myelin-like structure in the mitochondrial and Golgi complex organelles. In the case of the amastigote form, the specificity of the AgNP-PVP-MA nanocomposite was predominant by ultrastructural alterations in the flagellum, vacuole and flagellar pocket, with presence of nanocomposite in vesicles and close to the subpellicular microtubule, showing promoted possibly an mechanism of action directed by specific parasite organelles of Leishmania and its potential as a new treatment alternative for cutaneous leishmaniasis disease with the stimulation of a Th1 response. ROS: reactive oxygen species. NO: nitric oxide. TNF-α: tumor necrosis factor alpha. IL-4: Interleukin 4. IL-6: Interleukin 6. IL-17 A: Interleukin 17 A. MIP-1α: macrophage inflammatory protein-1 alpha. iNOS₂: inducible nitric oxide synthase 2. AgNP: silver nanoparticles