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Leishmania spp. cause a wide range of human diseases, localized skin lesions, mucocutaneous and visceral infections. In the present study, the aim was to investigate the potential role of sanguinarine as a specific inhibitor of Leishmania PP2C that can induce apoptosis in the parasite. The results demonstrated that sanguinarine inhibits, in a dose-dependent mode at 72 h, the growth and phosphatase activity of both Leishmania major and Leishmania mexicana promastigotes. Therefore, all assays were performed from this time period onwards. TUNEL assay was used to identify apoptosis and indicated apoptosis in L. major and L. mexicana promastigotes. Similarly, Western blot assay showed that PARP, a DNA damage indicator molecule, was present in L. major and L. mexicana promastigotes incubated with the inhibitor. In addition, differential expression of the proapoptotic protein Bax and the antiapoptotic protein Bcl-2 was observed in both Leishmania species. Finally, the protein phosphatase PP2C expression was not affected, whereas p38 MAPK phosphorylation was increased in L. major promastigotes than in L. mexicana promastigotes. Therefore, sanguinarine proved to be an inhibitor of the growth and PP2C enzymatic activity of L. major and L. mexicana promastigotes, and with it, this inhibition induced apoptosis., Competing Interests: Declarations. Competing Interests: The authors declare no competing interests., (© 2024. The Author(s).)

Dendritic cells (DC) are one of the principal host cells of the obligate intracellular parasite Leishmania. Inhibition of host cell apoptosis is a strategy employed by multiple pathogens to ensure their survival in the infected cell. We have previously shown that the infection of monocyte-derived dendritic cells (moDC) with Leishmania mexicana inhibits campthotecin-induced apoptosis. Nevertheless, the mechanisms involved in the inhibition of apoptosis of dendritic cells by Leishmania have not been established. Mitogen-activated protein kinases (MAPK) are key participants in the process of apoptosis and different species of Leishmania have been shown to regulate these kinases. In the present study, we analyzed the effect of L. mexicana promastigotes in the activation of JNK and p38 MAP kinase and their participation in the inhibition of apoptosis. The infection of moDC with L. mexicana promastigotes diminished significantly the phosphorylation of the MAP kinases JNK and p38. The inhibition of both kinases diminished DNA fragmentation, but in a major extent was the reduction of DNA fragmentation when JNK was inhibited. The capacity of L. mexicana promastigotes to diminish MAP kinases activation is probably one of the strategies employed to delay apoptosis induction in the infected moDC and may have implications for Leishmania pathogenesis by favoring the invasion of its host and the persistence of the parasite in the infected cells., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Leishmania mexicana is the causal agent of cutaneous leishmaniasis in Mexico. Dendritic cells (DC) are one of the host cells of Leishmania parasites. Intracellular microorganisms inhibit host cell apoptosis as a strategy to ensure their survival in infected cells. We have previously shown that Leishmania mexicana promastigotes and amastigotes inhibit camptothecin-induced apoptosis of monocyte-derived dendritic cells (moDC), but the mechanisms underlying the inhibition of apoptosis of DC by Leishmania have not been established. MAP kinases and PI3K participate in the process of apoptosis and are modulated by different species of Leishmania. As shown in this study, the infection of moDC with L. mexicana amastigotes diminished significantly the phosphorylation of the MAP kinases p38 and JNK. The inhibition of both kinases diminished significantly DNA fragmentation in moDC stimulated with camptothecin. On the other hand, L. mexicana amastigotes were able to activate the anti-apoptotic pathways PI3K and AKT. Our results indicate that L. mexicana amastigotes have the capacity to diminish MAP kinases activation and activate PI3K and AKT, which is probably one of the strategies employed by L. mexicana amastigotes to inhibit apoptosis in the infected moDC., (© 2015 John Wiley & Sons Ltd.)

Macrophages (Mphi) and dendritic cells (DC) are the major target cell populations of the obligate intracellular parasite Leishmania. Inhibition of host cell apoptosis is a method employed by multiple pathogens to ensure their survival in the infected cell. Leishmania has been shown to protect Mphi and neutrophils from both natural and induced apoptosis. As shown in this study, apoptosis in monocyte-derived dendritic cells (moDC) induced by treatment with camptothecin was downregulated by coincubation with L. mexicana, as detected by morphological analysis of cell nuclei, TUNEL assay, gel electrophoresis of low molecular weight DNA fragments, and annexin V binding to phosphatidylserine. The observed antiapoptotic effect was found to be associated with a significant reduction of caspase-3 activity in moDC. The capacity of L. mexicana to delay apoptosis induction in the infected moDC may have implications for Leishmania pathogenesis by favoring the invasion of its host and the persistence of the parasite in the infected cells.