Phagocytosis is inhibited by autophagic induction in murine macrophages.

Recent studies have demonstrated that communication takes place between the autophagic and phagocytic pathways, indicating that the convergence of these two pathways plays an important role in the innate immune response against intracellular microbes. The present study investigated the effect of autophagic induction on the phagocytic capacity of murine macrophages. Autophagy induced by physiological and pharmacological means was shown to reduce the phagocytic capacity of murine macrophages, regardless of cell origin or the nature of the phagocytosed particles themselves. This autophagic inhibitory effect on phagocytosis was shown to be an early and reversible event that results in no loss of cell viability. Furthermore, the data presented herein demonstrate that the induction of autophagy does not affect a macrophage's capacity to recognize and bind to particles, indicating that autophagy does not inhibit the particle recognition process, even though particle internalization is suppressed. The findings herein support the notion that phagocytosis and autophagy may be interdependent and complementary processes.

Differential properties of CBA/J mononuclear phagocytes recovered from an inflammatory site and probed with two different species of Leishmania.

While CBA/J mice fail to be permissive to Leishmania amazonensis-driven pathogenic processes, they heal easily following Leishmania major infection. The early-phase events are crucial to the outcome of Leishmania infection and it is known that macrophages (Mphi) are important in infection control. In the present study we investigated the role of Mphi in driving CBA/J susceptibility to L. amazonensis. We performed kinetic studies and compared the capacity of L. amazonensis and L. major to infect Mphi. There was no difference in percentages of infection or parasite burden for 6 h between the two groups. In contrast, after 12 h we observed that infection was about twice as high in L. amazonensis- than in L. major-infected Mphi. In addition, rIFN-gamma added to the cultures induced nitric oxide (NO) production, and did not modify L. amazonensis infection, although the percentage of L. major infection was significantly reduced. This reduction in L. major infection is a TNF-alpha dependent mechanism as L. major-infected Mphi expressed twice as much TNF-alpha mRNA as L. amazonensis-infected cells, and anti-TNF-alpha reversed the IFN-gamma effect. Moreover, rTNF-alpha plus IFN-gamma were able to significantly reduce the percentage of L. amazonensis-infected cells but not to the same extent as in L. major infection. Despite having higher NO production than IFN-gamma-treated cells, AMG addition to IFN-gamma-plus TNF-alpha-treated cells only partially reversed the inhibition in L. major, but not in L. amazonensis infection. Thus, in this study, we demonstrated that L. amazonensis both inactivated and resisted innate and IFN-gamma-induced Mphi killing mechanisms, indicating that the nature of the parasite and its interaction with Mphi could determine immune response polarization.

Estudo comparativo da infecção in vitro de macrófagos de camundongos CBA por Leishmania major e Leishmania amazonensis / Comparative study of in vitro CBA mice macrophages infection with L major and L. amazonensis

Camundongos da linhagem CBA são resistentes à infecção por L. major (Lm) e susceptíveis à infecção por L amazonensis (La), apresentando distintos padrões morfológicos da resposta tissular e da resposta imune. M desempenham importante papel na infecção por Leishmania por serem as principais células hospedeiras do parasito e uma das células apresentadoras de antígenos a linfócitos T específicos. Além disso, M uma vez ativados são capazes de destruir parasitos intemalizados por mecanismos dependentes da produção de NO. Nesse estudo o principal interesse foi investigar uma possível participação de M de camundongos CBA no estabelecimento da resposta imune durante as fases iniciais da infecção. Através de estudos de cinética foi avaliado o percentual de células infectadas pretratadas ou não com IFN-y. Para avaliar a sobrevivência e multiplicação do parasito no interior de M, foi determinado o número de parasitos /M em diferentes períodos de incubação. Através da mensuração dos níveis de NO foi avaliado a capacidade de M ativados em destruir parasitos intemalizados. Os resultados demonstram que entre 90 minutos e 12 horas após a adição de promastigotas, a proporção de M infectados e o número de parasitos/M foi similar em ambos os grupos. Entretanto, após o período de caça de 24 h o percentual de células infectadas por La foi 2 x mais elevado quando comparado à infecção por Lm. Essas diferenças foram mantidas após 48 e 72 h de caça. Nesses mesmos períodos o número de parasitos /M foi 2x maior em células infectadas por La que por Lm. Em células tratadas com IFN-y, após 24 horas de pulso o perfil de infecção apresentado em células não tratadas se manteve. Nesse mesmo período, em células infectadas por Lm a produção de NO teve uma elevação discreta comparado à infecção por La. Entretanto essa diferença não foi...