Dataset Information

Oxidative Stress-Mediated Overexpression of Uracil DNA Glycosylase in Leishmania donovani Confers Tolerance against Antileishmanial Drugs.

ABSTRACT: Leishmania donovani is an intracellular protozoan parasite that causes endemic tropical disease visceral leishmaniasis (VL). Present drugs used against this fatal disease are facing resistance and toxicity issues. Survival of leishmania inside the host cells depends on the parasite's capacity to cope up with highly oxidative environment. Base excision repair (BER) pathway in L. donovani remains unexplored. We studied uracil DNA glycosylase (UNG), the key enzyme involved in BER pathway, and found that the glycosylase activity of recombinant LdUNG (Leishmania donovani UNG) expressed in E. coli is in sync with the activity of the parasite lysate under different reaction conditions. Overexpression of UNG in the parasite enhances its tolerance towards various agents which produce reactive oxygen species (ROS) and shows a higher infectivity in macrophages. Surprisingly, exposure of parasite to amphotericin B and sodium antimony gluconate upregulates the expression of UNG. Further, we found that the drug resistant parasites isolated from VL patients show higher expression of UNG. Mechanisms of action of some currently used drugs include accumulation of ROS. Our findings strongly suggest that targeting LdUNG would be an attractive therapeutic strategy as well as potential measure to tackle the problem of drug resistance in the treatment of leishmaniasis.

SUBMITTER: Mishra A

PROVIDER: S-EPMC5845521 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Oxidative Stress-Mediated Overexpression of Uracil DNA Glycosylase in Leishmania donovani Confers Tolerance against Antileishmanial Drugs.

Mishra Anshul A Khan Mohd Imran MI Jha Pravin K PK Kumar Ajay A Das Sushmita S Das Prolay P Das Pradeep P Sinha Kislay K KK

Oxidative medicine and cellular longevity 20180225

Leishmania donovani is an intracellular protozoan parasite that causes endemic tropical disease visceral leishmaniasis (VL). Present drugs used against this fatal disease are facing resistance and toxicity issues. Survival of leishmania inside the host cells depends on the parasite's capacity to cope up with highly oxidative environment. Base excision repair (BER) pathway in L. donovani remains unexplored. We studied uracil DNA glycosylase (UNG), the key enzyme involved in BER path ...[more]

PMID: 29636843

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Project description:Leishmaniasis is a serious medical issue in many countries around the World, but it remains largely neglected in terms of research investment for developing new control and treatment measures. No vaccines exist for human use, and the chemotherapeutic agents currently used are scanty. Furthermore, for some drugs, resistance and treatment failure are increasing to alarming levels. The aim of this work was to identify genomic and trancriptomic alterations associated with experimental resistance against the common drugs used against VL: trivalent antimony (SbIII, S line), amphotericin B (AmB, A line), miltefosine (MIL, M line) and paromomycin (PMM, P line). A total of 1006 differentially expressed transcripts were identified in the S line, 379 in the A line, 146 in the M line, and 129 in the P line. Also, changes in ploidy of chromosomes and amplification/deletion of particular regions were observed in the resistant lines regarding the parental one. A series of genes were identified as possible drivers of the resistance phenotype and were validated in both promastigotes and amastigotes from Leishmania donovani, Leishmania infantum and Leishmania major species. Remarkably, a deletion of the gene LinJ.36.2510 (coding for 24-sterol methyltransferase, SMT) was found to be associated with AmB-resistance in the A line. In the P line, a dramatic overexpression of the transcripts LinJ.27.T1940 and LinJ.27.T1950 that results from a massive amplification of the collinear genes was suggested as one of the mechanisms of PMM resistance. This conclusion was reinforced after transfection experiments in which significant PMM-resistance was generated in WT parasites over-expressing either gene LinJ.27.1940 (coding for a D-lactate dehydrogenase-like protein, D-LDH) or gene LinJ.27.1950 (coding for an aminotransferase of branched-chain amino acids, BCAT). This work allowed to identify new drivers, like SMT, the deletion of which being associated with resistance to AmB, and the tandem D-LDH-BCAT, the amplification of which being related to PMM resistance.

Project description:BackgroundThere is a pressing need for drug discovery against visceral leishmaniasis, a life-threatening protozoal infection, as the available chemotherapy is antiquated and not bereft of side effects. Plants as alternate drug resources has rewarded mankind in the past and aimed in this direction, we investigated the antileishmanial potential of Cinnamomum cassia.MethodologyDichloromethane, ethanolic and aqueous fractions of C. cassia bark, prepared by sequential extraction, were appraised for their anti-promastigote activity along with apoptosis-inducing potential. The most potent, C. cassia dichloromethane fraction (CBD) was evaluated for anti-amastigote efficacy in infected macrophages and nitric oxide (NO) production studied. The in vivo antileishmanial efficacy was assessed in L. donovani infected BALB/c mice and hamsters and various correlates of host protective immunity ascertained. Toxicity profile of CBD was investigated in vitro against peritoneal macrophages and in vivo via alterations in liver and kidney functions. The plant secondary metabolites present in CBD were identified by gas chromatography-mass spectroscopy (GC-MS).Principal findingsCBD displayed significant anti-promastigote activity with 50% inhibitory concentration (IC50) of 33.6 ?g ml-1 that was mediated via apoptosis. This was evidenced by mitochondrial membrane depolarization, increased proportion of cells in sub-G0-G1 phase, ROS production, PS externalization and DNA fragmentation (TUNEL assay). CBD also inhibited intracellular amastigote proliferation (IC50 14.06 ?g ml-1) independent of NO production. The in vivo protection achieved was 80.91% (liver) and 82.92% (spleen) in mice and 75.61% (liver) and 78.93% (spleen) in hamsters indicating its profound therapeutic efficacy. CBD exhibited direct antileishmanial activity, as it did not specifically induce a T helper type (Th)-1-polarized mileu in cured hosts. This was evidenced by insignificant modulation of NO production, lymphoproliferation, DTH (delayed type hypersensitivity), serum IgG2a and IgG1 levels and production of Th2 cytokines (IL-4 and IL-10) along with restoration of pro-inflammatory Th1 cytokines (INF-?, IL-12p70) to the normal range. CBD was devoid of any toxicity in vitro as well as in vivo. The chemical constituents, cinnamaldehyde and its derivatives present in CBD may have imparted the observed antileishmanial effect.ConclusionsOur study highlights the profound antileishmanial efficacy of C. cassia bark DCM fraction and merits its further exploration as a source of safe and effective antieishmanial compounds.

Project description:Visceral leishmaniasis (VL) is a fatal parasitic disease if untreated. Treatment options of VL diminish due to emerging drug resistance. Although the principal host cells for the multiplication of Leishmania are macrophages, neutrophils are the first cells infected with the parasites rapidly after parasite inoculation. Leishmania can survive in neutrophils despite the potent antimicrobial effector functions of neutrophils that can eliminate the parasites. Recently, the growing field of immunometabolism provided strong evidence for the therapeutic potential in targeting metabolic processes as a means of controlling immune effector functions. Therefore, the understanding of the immunometabolic profile of neutrophils during Leishmania infection could provide new promising targets for host-directed therapies against VL. To our knowledge, this is the first study addressing the bioenergetics profile of L. donovani-infected primary human neutrophils. Transcriptome analysis of L. donovani-infected neutrophils revealed an early significant upregulation of several glycolytic enzymes. Extracellular flux analysis showed that glycolysis and glycolytic capacity were upregulated in L. donovani-infected neutrophils at 6 h post infection. An increased glucose uptake and accumulation of glycolytic end products were further signs for an elevated glycolytic metabolism in L. donovani-infected neutrophils. At the same time point, oxidative phosphorylation provided NADPH for the oxidative burst but did not contribute to ATP production. Inhibition of glycolysis with 2-DG significantly reduced the survival of L. donovani promastigotes in neutrophils and in culture. However, this reduction was due to a direct antileishmanial effect of 2-DG and not a consequence of enhanced antileishmanial activity of neutrophils. To further address the impact of glucose metabolism during the first days of infection in vivo, we treated C57BL/6 mice with 2-DG prior to infection with L. donovani and assessed the parasite load one day and seven days post infection. Our results show, that seven days post-infection the parasite load of 2-DG treated animals was significantly higher than in mock treated animals. This data indicates that glycolysis serves as major energy source for antimicrobial effector functions against L. donovani. Inhibition of glycolysis abrogates important neutrophil effector functions that are necessary the initial control of Leishmania infection.

Project description:Two dimensional (2D) NMR and molecular dynamics simulations have been used to determine the three dimensional (3D) structure of a hairpin DNA, d-CTA-GAGGATCC-TUTT-GGATCCT (22mer; abbreviated as U2-hairpin), which has uracil at the second position from the 5' end of the tetraloop. The(1)H resonances of this hairpin have been assigned almost completely. NMR restrained molecular dynamics and energy minimization procedures have been used to describe the 3D structure of U2-hairpin. This study establishes that the stem of the hairpin adopts a right-handed B-DNA conformation, while the T(12)and T(15)nucleotides stack upon 3' and 5' ends of the stem, respectively. Further, T(14)stacks upon both T(12)and T(15). Though U(13)partially stacks upon T(14), no stacking interaction is observed between U(13)and T(12). All the individual nucleotide bases belonging to the stem and T(12)and T(15)of the loop adopt ' anti ' conformation with respect to their sugar moiety, while the U(13)and T(14)of the loop are in ' syn ' conformation. The turning phosphate in the loop is located between T(13)and T(14). This study and a concurrent NMR structural study on yet another hairpin DNA d-CTAGAGGAATAA-TTTU-GGATCCT (22mer; abbreviated as U4-hairpin), with uracil at the fourth position from the 5' end of the tetraloop throw light upon various interactions which have been reported between Escherichia coli uracil DNA glycosylase (UDG) and uracil containing DNA. The epsilon of T(12)and alpha, beta, gamma, epsilon and zeta of U(13)and gamma of T(14), which partially influence the local conformation of U(13)in U2-hairpin are all locked in ' trans ' conformation. Such stretched out backbone conformation in the vicinity of U(13)could be the reason as to why the U2-hairpin is found to be the poor substrate for its interaction with UDG compared to the other substrates in which the uracil is at first, third and fourth positions of the tetraloop from its 5' end, as reported earlier by Vinay and Varshney. This study shows that UDG actively promotes the flipping of uracil from a stacked conformation and rules out the possibility of UDG recognizing the flipped out uracil bases.

Dataset Information

Oxidative Stress-Mediated Overexpression of Uracil DNA Glycosylase in Leishmania donovani Confers Tolerance against Antileishmanial Drugs.

Publications

Oxidative Stress-Mediated Overexpression of Uracil DNA Glycosylase in <i>Leishmania donovani</i> Confers Tolerance against Antileishmanial Drugs.

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