iridoids and Leishmaniasis--Visceral

To evaluate the antileishmanial efficacy of genipin, which specifically inhibits uncoupling protein 2 (UCP2) that is induced in leishmaniasis to neutralize reactive oxygen species (ROS).. The effect of genipin was assessed against intracellular parasites in cultured macrophages and in suppressing spleen and liver parasite burdens in a BALB/c mouse model of visceral leishmaniasis by microscopic evaluation of intracellular amastigotes stained with Giemsa. ROS and mitochondrial membrane potential were measured by H2DCFDA- and JC-1-based fluorometric analysis. ELISA was performed for various Th1 and Th2 cytokines in both in vitro and in vivo infected conditions to evaluate the type of immunological responses. The role of UCP2 was assessed by lipofectamine-mediated transfection and overexpression in macrophages and short hairpin RNA-mediated knockdown of UCP2 in infected animals.. Genipin reduced the infection-induced UCP2 levels in macrophages, with optimum effect at 100 μM. Genipin reversed parasite-induced ROS suppression and mitochondrial membrane potential disruption. It has no inhibitory effect on promastigote or axenic amastigote forms, but markedly suppressed amastigote multiplication within macrophages, which was reversed by the ROS scavenger N-acetyl cysteine. Genipin administration (30 mg/kg/day) in infected mice showed significant suppression of liver and spleen parasite burdens with an enhanced host-favourable cytokine balance in a ROS-p38 mitogen-activated protein kinase-dependent manner. Co-treatment with genipin plus a sublethal dose of sodium antimony gluconate (SAG50) showed almost a curative reduction in spleen and liver parasite burden.. These results suggest the effectiveness of genipin as a synergistic agent for the front-line antileishmanial drug SAG in circumventing the resistance and toxicity problems associated with its high curative dose.

Topics: Animals; Immunologic Factors; Iridoids; Leishmaniasis, Visceral; Mice; Mice, Inbred BALB C; Pharmaceutical Preparations; Reactive Oxygen Species; Uncoupling Protein 2

Much research effort has been focused on investigating new compounds derived from low-cost sources, such as natural products, for treating leishmaniasis. Oleuropein derived from numerous plants, particularly from the olive tree, Olea europaea L. (Oleaceae), is a biophenol with many biological activities. Our previous findings showed that oleuropein exhibits leishmanicidal effects against three Leishmania spp. in vitro, and minimizes the parasite burden in L. donovani-infected BALB/c mice. The aim of the present study is to investigate the possible mechanism(s) that mediate this leishmanicidal activity.. We determined the efficacy of oleuropein in elevating ROS and NO production in L. donovani-infected J774A.1 macrophages and in explanted splenocytes and hepatocytes obtained from L. donovani-infected BALB/c mice. We also assessed the expression of genes that are related to inflammation, T-cell polarization and antioxidant defense, in splenocytes. Finally, we determined the ratios of specific IgG2a/IgG1 antibodies and DTH reactions in L. donovani-infected BALB/c mice treated with oleuropein.. Oleuropein was able to elevate ROS production in both in vitro and in vivo models of visceral leishmaniasis and raised NO production in ex vivo cultures of splenocytes and hepatocytes. The extensive oxidative stress found in oleuropein-treated mice was obviated by the upregulation of the host's antioxidant enzyme (mGCLC) and the simultaneous downregulation of the corresponding enzyme of the parasite (LdGCLC). Moreover, oleuropein was able to mount a significant Th1 polarization characterized by the expression of immune genes (IL-12β, IL-10, TGF-β1, IFN-γ) and transcription factors (Tbx21 and GATA3). Moreover, this immunomodulatory effect was also correlated with an inhibitory effect on IL-1β gene expression, rather than with the expression of IL-1α, IL-1rn and TNF-α. Furthermore, oleuropein-treated BALB/c mice mounted a delayed-type hypersensitivity (DTH) response and an elevated Leishmania-specific IgG2a/IgG1 ratio that clearly demonstrated an in vivo protective mechanism.. The ability of Oleuropein to promote a Th1 type immune response in L. donovani-infected BALB/c mice points towards the candidacy of this bioactive compound as an immunomodulatory agent that may complement therapeutic approaches to leishmaniasis.

Topics: Animals; Antiprotozoal Agents; Female; Humans; Interferon-gamma; Interleukin-10; Iridoid Glucosides; Iridoids; Leishmania donovani; Leishmaniasis, Visceral; Macrophages; Mice; Mice, Inbred BALB C; Olea; Oxidative Stress; Plant Extracts; Th1 Cells; Transforming Growth Factor beta1

The antileishmanial property of amarogentin, a secoiridoid glycoside isolated from the Indian medicinal plant Swertia chirata, was examined in a hamster model of experimental leishmaniasis. The therapeutic efficacy of amarogentin was evaluated in free and two different vesicular forms, liposomes and niosomes. The amarogentin in both liposomal and niosomal forms was found to be a more active leishmanicidal agent than the free amarogentin; and the niosomal form was found to be more efficacious than the liposomal form at the same membrane microviscosity level. Toxicity studies involving blood pathology, histological staining of tissues and specific enzyme levels related to normal liver function showed no toxicity. Hence, amarogentin incorporated in liposomes or niosomes may have clinical application in the treatment of leishmaniasis.

Topics: Alanine Transaminase; Alkaline Phosphatase; Animals; Antiprotozoal Agents; Cricetinae; Drug Carriers; Glucosides; Iridoids; Leishmania donovani; Leishmaniasis, Visceral; Liposomes; Mesocricetus; Pyrans; Spleen; Surface-Active Agents; Treatment Outcome