The combination of FLT3 and DNA methyltransferase inhibition is synergistically cytotoxic to FLT3/ITD acute myeloid leukemia cells

Effective treatment regimens for elderly acute myeloid leukemia (AML) patients harboring internal tandem duplication mutations in the FMS-like tyrosine kinase-3 (FLT3) gene (FLT3/ITD) are lacking and represent a significant unmet need. Recent data on the effects of FLT3 tyrosine kinase inhibitors on FLT3/ITD+ AML showed promising clinical activity, including in elderly patients. DNA methyltransferase (DNMT) inhibitors such as decitabine (5-aza-2-deoxycytidine, DEC) and 5-azacitidine (AZA) demonstrated clinical benefit in AML, are well tolerated and are associated with minimal increases in FLT3 ligand, which can represent a potential resistance mechanism to FLT3 inhibitors. In addition, both FLT3 and DNMT inhibition are associated with the induction of terminal differentiation of myeloid blasts. Consequently, there is a strong theoretical rationale for combining FLT3 and DNMT inhibition for FLT3/ITD+ AML. We therefore sought to study the anti-leukemic effects of DEC, AZA and FLT3 inhibitors, either as single agents or in combination, on AML cell lines and primary cells derived from newly diagnosed and relapsed AML patients. Our studies indicate that combined treatment using FLT3 inhibition and hypomethylation confers synergistic anti-leukemic effects, including apoptosis, growth inhibition and differentiation. The simultaneous administration of AZA and FLT3 inhibition appears to be the most efficacious combination in this regard. These drugs may provide a novel therapeutic approach for FLT3/ITD+ AML, in particular for older patients

41 Elevated Levels of IL-10 in CD3⁺ CD8⁺ Lymphocytes and Immunoglobulin G3 Characterize Indian post kala-azar Dermal leishmaniasis

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Development of a semi-automated colorimetric assay for screening anti-leishmanial agents

MTS or {3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl}-2H-tetrazolium, inner salt) is converted into soluble formazan by mitochondrial dehydrogenase of viable cells, thus serving as an indicator of cell viability. Accordingly, a MTS-based assay was developed to evaluate anti-leishmanial activity in Leishmania promastigotes from strains responsible for visceral, cutaneous or mucocutaneous leishmaniasis. The assay was initially optimized for the appropriate wavelength (490 nm), culture medium (M-199), incubation time (3 h) and temperature (37 °C). Increasing absorbance with increasing cell density confirmed linearity of the assay that was maintained up to 2.5 × 106 cells/200 μl. The growth kinetics of six L. donovani strains and six non-L. donovani strains consistently indicated higher absorbances in the L. donovani strains highlighting the importance of strain-specific customization of the MTS assay. The IC50 values (i.e., the concentration at which 50% of growth was inhibited) of amphotericin B, miltefosine and pentamidine isethionate obtained by the MTS assay corroborated with previously published data. Taken together, the MTS assay thus permits a simple, reproducible and reliable semi-automated method for evaluating cell viability, effective for drug-screening and growth kinetic studies

An ethanol extract of Piper betle Linn. mediates its anti-inflammatory activity via down-regulation of nitric oxide

The leaves of Piper betle (locally known as Paan) have long been in use in the Indian indigenous system of medicine for the relief of pain; however, the underlying molecular mechanisms of this effect have not been elucidated. The anti-inflammatory and immunomodulatory effects of an ethanolic extract of the leaves of P. betle (100 mg kg−1; PB) were demonstrated in a complete Freund's adjuvant-induced model of arthritis in rats with dexamethasone (0.1 mg kg−1) as the positive control. At non-toxic concentrations of PB (5–25 μg mL−1), a dose-dependent decrease in extracellular production of nitric oxide in murine peritoneal macrophages was measured by the Griess assay and corroborated by flow cytometry using the nitric oxide specific probe, 4,5-diaminofluorescein-2 diacetate. This decreased generation of reactive nitrogen species was mediated by PB progressively down-regulating transcription of inducible nitric oxide synthase in macrophages, and concomitantly causing a dose-dependent decrease in the expression of interleukin-12 p40, indicating the ability of PB to down-regulate T-helper 1 pro-inflammatory responses. Taken together, the anti-inflammatory and anti-arthrotic activity of PB is attributable to its ability to down-regulate the generation of reactive nitrogen species, thus meriting further pharmacological investigation

Efficacy of artemisinin in experimental visceral leishmaniasis

Visceral leishmaniasis (VL), caused by the protozoan Leishmania sp., affects 500 000 people annually, with the Indian subcontinent contributing a significant proportion of these cases. Emerging refractoriness to conventional antimony therapy has emphasised the need for safer yet effective antileishmanial drugs. Artemisinin, a widely used antimalarial, demonstrated anti-promastigote activity and the 50% inhibitory concentration (IC₅₀) ranged from 100 μM to 120 μM irrespective of Leishmania species studied. Leishmaniadonovani-infected macrophages demonstrated decreased production of nitrite as well as mRNA expression of inducible nitric oxide synthase, which was normalised by artemisinin, indicating that it exerted both a direct parasiticidal activity as well as inducing a host protective response. Furthermore, in a BALB/c model of VL, orally administered artemisinin (10 mg/kg and 25 mg/kg body weight) effectively reduced both splenic weight and parasite burden, which was accompanied by a restoration of Th1 cytokines (interferon-gamma and interleukin-2). Taken together, these findings have delineated the therapeutic potential of artemisinin in experimental VL

Iron enhances generation of free radicals by Artemisinin causing a caspase-independent, apoptotic death in Leishmania donovani promastigotes

An increasing incidence of unresponsiveness to antimonials in Leishmaniasis has led to identification of plant-derived anti-leishmanial compounds like Artemisinin. Since iron-mediated generation of free radicals sustains the anti-malarial activity of Artemisinin, this study investigated whether similar mechanisms accounted for its activity in Leishmania promastigotes. Artemisinin effectively disrupted the redox potential via an increased generation of free radicals along with a decrease in levels of non-protein thiols. Attenuation of its IC50 by a free radical scavenger N-acetyl l-cysteine and an iron chelator desferoxamine established the pivotal role of free radicals and of the potentiating effect of iron. An enhanced Fluo-4 fluorescence reflected Artemisinin-induced mobilization of intracellular calcium, which triggered apoptosis. However, the absence of any detectable caspase activity indicated that the leishmanicidal activity of Artemisinin is mediated by an iron-dependent generation of reactive intermediates, terminating in a caspase-independent, apoptotic mode of cell death

Post-kala-azar dermal leishmaniasis - an overview

Post-kala-azar dermal leishmaniasis (PKDL) is a dermal sequela of visceral leishmaniasis (VL), reported mainly from two regions – Sudan in eastern Africa and the Indian subcontinent, with incidences of 50–60% and 5–10%, respectively. Importantly, patients with PKDL are considered as reservoirs of VL, linking its eradication to effective control of PKDL. The etiopathogenesis of PKDL is presumably due to an immunological assault on latent dermal parasites. Immunological markers include IL-10, whose expression in skin and plasma of Sudanese patients with VL predicted onset of PKDL. Cell-mediated immune responses, notably restoration of IFN-γ production by antigen-stimulated lymphocytes are well documented in Sudanese PKDL, but remain ambiguous in the Indian form; recently, antigen-specific IL-10-producing CD8+ lymphocytes have been implicated in pathogenesis. In Indian PKDL, upregulation of intralesional IFN-γ and TNF-α is counterbalanced by IL-10 and TGF-β together with downregulated IFN-γ R1. Although IL-10 curtails excessive IFN-γ-mediated reactivity and ensures parasite survival, its cellular source remains to be confirmed, with infiltrating regulatory T cells (Tregs) being a likely candidate. Future functional investigations on Tregs and their interaction with lesional effector lymphocytes would be indispensable for development of immunomodulatory therapies against Leishmania infection

Artemisinin triggers induction of cell-cycle arrest and apoptosis in Leishmania donovani promastigotes

A major impediment to effective anti-leishmanial chemotherapy is the emergence of drug resistance, especially to sodium antimony gluconate, the first-line treatment for leishmaniasis. Artemisinin, a sesquiterpene lactone isolated from Artemisia annua, is an established anti-malarial compound that showed anti-leishmanial activity in both promastigotes and amastigotes, with IC50 values of 160 and 22 μM, respectively, and, importantly, was accompanied by a high safety index (>22-fold). The leishmanicidal activity of artemisinin was mediated via apoptosis as evidenced by externalization of phosphatidylserine, loss of mitochondrial membrane potential, in situ labelling of DNA fragments by terminal deoxyribonucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) and cell-cycle arrest at the sub-G0/G1 phase. Taken together, these data indicate that artemisinin has promising anti-leishmanial activity that is mediated by programmed cell death and, accordingly, merits consideration and further investigation as a therapeutic option for the treatment of leishmaniasis

High-throughput screening of amastigotes of <i>Leishmania donovani </i>clinical isolates against drugs using a colorimetric β-lactamase assay

475-479A simple colorimetric β-lactamase assay for quantifying Leishmania amastigotes in macrophages grown in microtiter plates has been reported. The β-lactamase gene was integrated into the rRNA region of the genome, thereby allowing for high-level stable expression of the enzyme. Both visceral leishmaniasis (VL) and post-kala azar dermal leishmaniasis (PKDL) isolates were transfected with β-Lactamase gene. These β-lactamase-expressing promastigotes were used for infecting intracellular J774A.1 macrophages in vitro. Quantification was done by a colorimetric readout with CENTATM β-lactamase as substrate and with an optical density plate reader. The assay was carried out in 96-well plates. Results obtained demonstrate that this methodology could be a valuable high-throughput screening assay for checking efficacy of anti-leishmanial drugs in the clinical isolates

Cytotoxicity of Senecio in macrophages is mediated via its induction of oxidative stress

In Arunachal Pradesh and other sub-Himalayan areas of India, accidental consumption of Senecio plants by yaks is often fatal as the plant contains toxic alkaloids like Seneciophylline. The present investigation was undertaken to demonstrate the pro-oxidant effects of an ethanolic extract of Seneciochrysanthemoides (S-EtOH). S-EtOH impaired viability in macrophages, the IC50 being 13.8 ± 1.11 μg/mL. The effect of S-EtOH (1 μg/mL) on generation of reactive oxygen species (ROS) in macrophages was measured by flow cytometry using 2′,7′-dichlorofluorescein diacetate (H2DCFDA) where it caused a significant increase in the mean fluorescence channel (MFC) from 8.55 ± 0.03 to 47.32 ± 2.25 (p < 0.001). S-EtOH also effected a 3.8-fold increase in extracellular nitric oxide (NO) generation from 4.90 ± 0.72 μM to 18.79 ± 0.32 μM (p < 0.001), a 2.2-fold increase in intracellular NO production, the MFC increasing from 14.95 ± 0.48 to 33.34 ± 1.66 (p < 0.001), and concomitantly depleted non protein thiols as analyzed by flow cytometry using mercury orange, with a reduction in MFC from 632.5 ± 49.44 to 407.4 ± 12.61 (p < 0.01). Additionally, S-EtOH (14 μg/mL, 24 h) caused apoptosis as evident by increased Annexin V binding and terminal deoxynucleotidyl transferase mediated dUTP DNA nick end labeling. Taken together, the cytotoxicity of S-EtOH can be partly attributed to its capacity to inflict oxidative damage via generation of both reactive oxygen and nitrogen species culminating in apoptosis