Melittin induces in vitro death of Leishmania (Leishmania) infantum by triggering the cellular innate immune response

Background: Apis mellifera venom, which has already been recommended as an alternative anti-inflammatory treatment, may be also considered an important source of candidate molecules for biotechnological and biomedical uses, such as the treatment of parasitic diseases. Methods: Africanized honeybee venom from Apis mellifera was fractionated by RP-C18-HPLC and the obtained melittin was incubated with promastigotes and intracellular amastigotes of Leishmania (L.) infantum. Cytotoxicity to mice peritoneal macrophages was evaluated through mitochondrial oxidative activity. The production of anti-and pro-inflammatory cytokines, NO and H2O2 by macrophages was determined. Results: Promastigotes and intracellular amastigotes were susceptible to melittin (IC50 28.3 mu g.mL(-1) and 1.4 mu g.mL(-1), respectively), but also showed mammalian cell cytotoxicity with an IC50 value of 5.7 mu g.mL(-1). Uninfected macrophages treated with melittin increased the production of IL-10, TNF-alpha, NO and H2O2. Infected melittin-treated macrophages increased IL-12 production, but decreased the levels of IL-10, TNF-alpha, NO and H2O2. Conclusions: The results showed that melittin acts in vitro against promastigotes and intracellular amastigotes of Leishmania (L.) infantum. Furthermore, they can act indirectly on intracellular amastigotes through a macrophage immunomodulatory effect

Silicon influence on resistance induction against Bemisia tabaci biotype B (Genn.) (Hemiptera: Aleyrodidae) and on vegetative development in two soybean cultivars

The potential of populations of Bemisia tabaci (Genn.) to become resistant to insecticides has stimulated research into alternative tactics of integrated pest management such as the induction of host-plant resistance. Recent data have shown that silicon can increase the degree of resistance of host plants to insect pests. Therefore the aim of our work was to study the effects of silicon application on the vegetative development of soybean plants and on the induction of resistance to the silverleaf whitefly, B. tabaci biotype B. We performed choice and no-choice tests of oviposition preference on two soybean cultivars, IAC-19 (moderately resistant to B. tabaci biotype B) and MONSOY-8001 (susceptible), with and without application of silicon. Silicon did not affect silverleaf whitefly oviposition preferences, but caused significant mortality in nymphs. Thus, silicon increased the degree of resistance to silverleaf whitefly. Silicon decreased the production of phenolic compounds, but did not affect lignin production. However, when applied to cultivar IAC-19, it increased the production of non-protein organic nitrogen. Silicon had no effect on the vegetative development of soybean plants, but it increased the degree of resistance to the silverleaf whitefly. We conclude that silicon applications combined with cultivar IAC-19 can significantly decrease silverleaf whitefly populations, having a positive impact both on the soybean plant and on the environment.