NLRP1-dependent activation of Gasdermin D in neutrophils controls cutaneous leishmaniasis.

Intracellular pathogens that replicate in host myeloid cells have devised ways to inhibit the cell's killing machinery. Pyroptosis is one of the host strategies used to reduce the pathogen replicating niche and thereby control its expansion. The intracellular Leishmania parasites can survive and use neutrophils as a silent entry niche, favoring subsequent parasite dissemination into the host. Here, we show that Leishmania mexicana induces NLRP1- and caspase-1-dependent Gasdermin D (GSDMD)-mediated pyroptosis in neutrophils, a process critical to control the parasite-induced pathology. In the absence of GSDMD, we observe an increased number of infected dermal neutrophils two days post-infection. Using adoptive neutrophil transfer in neutropenic mice, we show that pyroptosis contributes to the regulation of the neutrophil niche early after infection. The critical role of neutrophil pyroptosis and its positive influence on the regulation of the disease outcome was further demonstrated following infection of mice with neutrophil-specific deletion of GSDMD. Thus, our study establishes neutrophil pyroptosis as a critical regulator of leishmaniasis pathology.

A mushroom derived 'carbohydrate-fraction' reinstates host-immunity and protects from Leishmania donovani infection.

The anti-leishmanial effect of the 'carbohydrate-fraction', isolated from an edible mushroom Astraeus hygrometricus, was evaluated against Leishmania donovani infection both in vitro and in vivo. Ahf-Car induced the expression of inducible nitric oxide synthase 2 (iNOS2) and pro-inflammatory cytokines like TNF-α and IL-12, with subsequent downregulation of the anti-inflammatory cytokines as TGF-ß and IL-10, in vitro and in vivo along with a remarkable increase in the expressions of IL-6, IL-1ß, IFN-γ and IRFs, IRF-7 and IRF-8 in vivo. Ahf-Car also reduced the parasite burden in the spleen and liver dose-dependently with a simultaneous proliferation of Ly6C+ cells in the bone marrow of Leishmania-infected experimental animals. It also increased the monocyte population dose-dependently and the expression of the myeloid transcription factor PU.1, in vivo, which presumably signifies the expansion of protective macrophages. Thus, Ahf-Car might be a potent anti-leishmanial lead with unique and effective adjuvant capacity.

Combination of Mycobacterium indicus pranii and Heat-Induced Promastigotes Cures Drug-Resistant Leishmania Infection: Critical Role of Interleukin-6-Producing Classical Dendritic Cells.

The major issues in available therapeutic modalities against leishmaniasis are cost, toxicity, and the emergence of drug resistance. The aim of this work was to develop a successful therapeutic adjuvant against drug-resistant Leishmania donovani infection by means of combining Mycobacterium indicus pranii with heat-induced promastigotes (HIP). One-month postinfected BALB/c mice were administered subcutaneously with M. indicus pranii (108 cells) and HIP (100 µg) for 5 days. Spleens were harvested for flow cytometric and reverse transcriptase PCR analysis. The antileishmanial effect of the combination strategy was associated with induction of a disease-resolving Th1 and Th17 response with simultaneous downregulation of CD4+ CD25+ Foxp3+ (nTreg) cells and CD4+ CD25- Foxp3- (Tr1) cells in the spleen. The significant expansion of CD4+ TCM (CD4+ CD44hi CD11ahi CD62Lhi) cells was a further interesting outcome of this therapeutic strategy in the context of long-term protection of hosts against secondary infection. Toll-like receptor 2 (TLR2) was also found instrumental in this antiparasitic therapy. Induced interleukin-6 (IL-6) production from expanded CD11c+ CD8α+ (cDC1) and CD11c+ CD11b+ (cDC2) dendritic cells (DCs) but not from the CD11b+ Ly6c+ inflammatory monocytes (iMOs), was found critical in the protective expansion of Th17 as evidenced by an in vivo IL-6 neutralization assay. It also promoted the hematopoietic conversion toward DC progenitors (pre-DCs) from common dendritic cell progenitors (CDPs), the immediate precursors, in bone marrow. This novel combinational strategy demonstrated that expansion of Th17 by IL-6 released from CD11c+ classical DCs is crucial, together with the conventional Th1 response, to control drug-resistant infection.

Selective in vitro inhibition of Leishmania donovani by a semi-purified fraction of wild mushroom Grifola frondosa.

The current study was designed to assess the anti-leishmanial effect of a semi-purified fraction of wild mushroom Grifola frondosa against Leishmania donovani, in vitro. A total of five extracts from three wild mushrooms [Grifola frondosa (family, Meripilaceae) Laetiporus sulphurous (family, Polyporaceae) and Meripilus giganteus (family, Meripilaceae) were explored for novel anti-leishmanial leads against promastigotes. The ethanol extract of G. frondosa was selected as the most efficient against L. donovani promastigotes (IC50: 93.9 µg/mL). A semi-purified fraction was obtained from an active ethanol extract of G. frondosa and found to inhibit the survival of promastigotes of L. donovani (MHOM/IN/83/AG83) significantly (IC50: 20.37 µg/mL) and it also had some effect against L. major LV39 (MRHO/Sv/59/P strain) and L. tropica WR683 (MHOM/SU/58/OD) strains at higher concentrations (IC50: 46.08 µg/mL and 53.79 µg/mL respectively). The semi-purified fraction also interfered in lipid biosynthesis, altered parasite morphology and induced apoptosis in L. donovani promastigotes. The semi-purified fraction was also effective against intracellular amastigotes in infected macrophages and enhanced the release of nitric oxide and pro-inflammatory cytokines, in vitro. Interestingly, the 50% inhibitory concentration of the semi-purified fraction against the intracellular amastigotes (IC50: 2.48 µg/mL) was much lower in comparison to promastigotes (IC50: 20.37 µg/mL). The semi-purified fraction was found to inhibit the intracellular amastigotes slightly more efficiently in comparison to conventional anti-leishmanial drugs; sodium antimony gluconate, amphotericin B, miltefosine and paromomycin and noticeably non-toxic towards host splenocytes. The findings of the present study established that G. frondosa might be a natural resource for development of a new anti-leishmanial lead.

Synthesis and biological evaluation of polyhydroxylated oxindole derivatives as potential antileishmanial agent.

The devastating appearance of numerous drug-unresponsive strains of Leishmania donovani and severe toxic side effects of conventional antileishmanial therapy necessitates the search for novel leads, to treat visceral leishmaniasis efficiently. The current study deals with the synthesis and biological evaluation of a unique C-5 functionalized oxindole based polyphenol to ascertain its activities against L. donovani infection, in vitro. The polyhydroxylated oxindole derivative (1) was generated by coupling styrene derivatives with 5-bromo bis-arylidene oxindole using Heck coupling reaction. The synthesized molecule 1 was tested for its antileishmanial activity using both promastigote and amastigote stages of L. donovani. Molecule 1 showed promising anti-promastigote and anti-amastigote activities with IC50 values 15 µM and 1 µM, respectively, with no cytotoxicity towards host splenocytes. The results revealed that this compound induced parasite death by promoting oxidative stress, thereby triggering apoptosis.

Successful Therapy of Murine Visceral Leishmaniasis with Astrakurkurone, a Triterpene Isolated from the Mushroom Astraeus hygrometricus, Involves the Induction of Protective Cell-Mediated Immunity and TLR9.

In our previous report, we showed that astrakurkurone, a triterpene isolated from the Indian mushroom Astraeus hygrometricus (Pers.) Morgan, induced reactive oxygen species, leading to apoptosis in Leishmania donovani promastigotes, and also was effective in inhibiting intracellular amastigotes at the 50% inhibitory concentration of 2.5 µg/ml. The aim of the present study is to characterize the associated immunomodulatory potentials and cellular activation provided by astrakurkurone, leading to effective antileishmanial activity in vitro and in vivo Astrakurkurone-mediated antileishmanial activity was evaluated by real-time PCR and flow cytometry. The involvement of Toll-like receptor 9 (TLR9) was studied by in vitro assay in the presence of a TLR9 agonist and antagonist and by in silico modeling of a three-dimensional structure of the ectodomain of TLR9 and its interaction with astrakurkurone. Astrakurkurone caused a significant increase in TLR9 expression of L. donovani-infected macrophages along with the activation of proinflammatory responses. The involvement of TLR9 in astrakurkurone-mediated amastigote killing has been evidenced from the fact that a TLR9 agonist (CpG, ODN 1826) in combination with astrakurkurone enhanced the amastigote killing, while a TLR9 antagonist (bafilomycin A1) alone or in combination with astrakurkurone curbed the amastigote killing, which could be further justified by in silico evidence of docking between mouse TLR9 and astrakurkurone. Astrakurkurone was found to reduce the parasite burden in vivo by inducing protective cytokines, gamma interferon and interleukin 17. Moreover, astrakurkurone was nontoxic toward peripheral blood mononuclear cells of immunocompromised patients with visceral leishmaniasis. Astrakurkurone, a nontoxic antileishmanial, enhances the immune efficiency of host cells, leading to parasite clearance in vitro and in vivo.

Induction of apoptosis by zerumbone isolated from Zingiber zerumbet (L.) Smith in protozoan parasite Leishmania donovani due to oxidative stress

Abstract In the present context of emergence of resistance aligned with the conventional anti-leishmanial drugs and occasional treatment failure compelled us to continue the search for replaceable therapeutic leads against Leishmaniainfection. Various ginger spices of the Zingiberaceae family are widely used as spices, flavouring agents, and medicines in Southeast Asia because of their unique flavour as well as due to their medicinal properties. Zerumbone, a natural component of Zingiber zerumbet (L.) Smith, has been studied for its pharmacological potential as antiulcer, antioxidant, anticancer, and antimicrobial. In this study, we have shown that zerumbone could induce ROS mediated apoptosis in Leishmania donovani promastigotes and also found effective in reducing intracellular amastigotes in infected-macrophages. We emphasized the potential of zerumbone to be employed in the development of new therapeutic drugs against L. donovaniinfection and provided the basis for future research on the application of transitional medicinal plants.

Induction of apoptosis by zerumbone isolated from Zingiber zerumbet (L.) Smith in protozoan parasite Leishmania donovani due to oxidative stress.

In the present context of emergence of resistance aligned with the conventional anti-leishmanial drugs and occasional treatment failure compelled us to continue the search for replaceable therapeutic leads against Leishmania infection. Various ginger spices of the Zingiberaceae family are widely used as spices, flavouring agents, and medicines in Southeast Asia because of their unique flavour as well as due to their medicinal properties. Zerumbone, a natural component of Zingiber zerumbet (L.) Smith, has been studied for its pharmacological potential as antiulcer, antioxidant, anticancer, and antimicrobial. In this study, we have shown that zerumbone could induce ROS mediated apoptosis in Leishmania donovani promastigotes and also found effective in reducing intracellular amastigotes in infected-macrophages. We emphasized the potential of zerumbone to be employed in the development of new therapeutic drugs against L. donovani infection and provided the basis for future research on the application of transitional medicinal plants.

Protective effect of Croton caudatus Geisel leaf extract against experimental visceral leishmaniasis induces proinflammatory cytokines in vitro and in vivo.

In the present state of overwhelming emergence of drug-unresponsive phenotypes of Leishmania donovani and persistent severe toxicity in conventional anti-leishmanial therapy, in search for novel leads, the aim of this study has been fixed to identify the active extract(s) of Croton caudatus Geisel. var. tomentosus Hook effective against the parasitic protozoans in vitro and in vivo. C. caudatus Geisel. is often used by Chakma and Hmar community, the local tribes of north-east India for medicinal and veterinary purposes. Among the five semi-purified extracts tested, C. caudatus leaves, extracted in hexane and subsequently semi-purified in a column packed with silica gel (70-130 µM; mesh size 60 A°) using ethyl acetate-hexane solvent (9:1), was found to be the most effective growth inhibitor (JDHex) against the Leishmania promastigotes and amastigotes. JDHex significantly altered the biochemical parameters (protein, lipid and carbohydrates) in promastigotes followed by the morphological changes, DNA condensation and subsequent apoptosis in L. donovani. In consequent steps, it has been also proved that JDHex reduced the replication of intracellular amastigotes with concomitant release of nitric oxide and pro-inflammatory cytokines, IL-12 and TNF-α in vitro. Significantly, the 50% inhibitory concentration of JDHex was estimated much lower against the intracellular amastigotes (2.5 µg/mL) in comparison to promastigotes (10 µg/mL). JDHex was also found efficient in reducing parasite burden in spleen and liver when treated in vivo and increased the intracellular IFN-γ and decreased the IL-10 in CD4+ T cells in splenocytes of orally treated animals. The results of this study support the importance in exploration of novel anti-leishmanial leads from C. caudatus Geisel. var. tomentosus Hook. against the L. donovani (MHOM/IN/83/AG83) infection. Partial chemical characterization of JDHex revealed the presence of terpenoids. However, the further chemical investigation of JDHex is warranted.

Selective inhibition of Leishmania donovani by active extracts of wild mushrooms used by the tribal population of India: An in vitro exploration for new leads against parasitic protozoans.

The study was intended at evaluating the anti-proliferating effect of mushrooms used in traditional folklore of Santal tribal population in India against Leishmania donovani (MHOM/IN/83/AG83). A total of eighteen extracts, three estracts from each mushroom [(80% ethanol extracted; Fa), (water-soluble polysaccharide fraction; Fb), (polyphenolic fraction; Fc)], from six wild mushrooms were obtained. These extracts were tested against the promastigotes and amastigotes for their antileishmanial capacity. Fa fractions (250 µg/mL) of Astraeus hygrometricus and Tricholoma giganteum significantly inhibited the growth of L. donovani promastigotes and interfered in lipid biosynthesis. Moreover, both fractions induced apoptosis in promastigotes. Water soluble Fb fractions of A. hygrometricus, Russula laurocerasi, Russula albonigra, Termitomyces eurhizus, Russula delica and polyphenolic Fc fraction of R. laurocerasi were found to inhibit the replication of intracellular amastigotes in macrophages dose dependently. Significantly, 50% inhibitory concentration of the active extracts against intracellular amastigotes induced release of nitric oxide and IL-12 in murine macrophages and dendritic cells assay and also found considerably non-toxic on murine splenocytes. Results of this study can be used as a basis for further phytochemical and pharmacological investigations in the effort for search of novel anti-leishmanial leads.

Chromone linked nitrone derivative induces the expression of iNOS2 and Th1 cytokines but reduces the Th2 response in experimental visceral leishmaniasis.

In our previous work we have shown that the novel synthetic chromone derivative could effectively inhibit the Leishmania donovani replication in vitro and in vivo with less cytotoxicity on murine splenocytes. The aim of the present study is to explore the possible mechanism of anti-leishmanial effect of C-(6-methyl-4-oxo-4H-1-benzopyran-3-yl)-N-(p-tolyl) nitrone (designated as NP1) in vitro and in vivo in experimental visceral leishmaniasis caused by L. donovani. The cytotoxic effect of this derivative was studied in murine peritoneal macrophages by MTT method. NP1 at a dose of 17.06 µM showed 50% inhibition on L. donovani promastigotes but found less cytotoxic to the RAW 264.7 cells. Even the higher concentration of IC50 (up to four fold) did not exert much cytotoxic effect on RAW 264.7. Interestingly, NP1 at lower concentration (8.53 µM) could inhibit 50% of intracellular amastigotes in murine peritoneal macrophages. L. donovani is known to exert its pathogenic effects mainly by the suppression of NO generation and subversion of the cellular inflammatory responses in the macrophages. NP1 was found to induce a potent host-protective immune response by enhancing NO generation and iNOS2 expression at mRNA level and by up-regulating proinflammatory cytokines such as IL-12 and IFN-γ and limiting the expression of IL-10 in vivo. The NO dependent killing was further confirmed in iNOS(-/-) mice compared to wild type. In agreement with the fact, induced synthesis of IL-12 and IFN-γ and associated down-regulation of IL-10 by the treatment of NP1 clearly indicated the possibility of novel strategy of drug development against Leishmania infection.