Dataset Information

Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

ABSTRACT: Previous work from our group showed that tamoxifen, an oral drug that has been in use for the treatment of breast cancer for over 40 years, is active both in vitro and in vivo against several species of Leishmania, the etiological agent of leishmaniasis. Using a combination of metabolic labeling with [³H]-sphingosine and myo-[³H]-inositol, alkaline hydrolysis, HPTLC fractionations and mass spectrometry analyses, we observed a perturbation in the metabolism of inositolphosphorylceramides (IPCs) and phosphatidylinositols (PIs) after treatment of L. amazonensis promastigotes with tamoxifen, with a significant reduction in the biosynthesis of the major IPCs (composed of d16:1/18:0-IPC, t16:0/C18:0-IPC, d18:1/18:0-IPC and t16:0/20:0-IPC) and PIs (sn-1-O-(C_18:0)alkyl -2-O-(C_18:1)acylglycerol-3-HPO₄-inositol and sn-1-O-(C_18:0)acyl-2-O-(C_18:1)acylglycerol-3-HPO₄-inositol) species. Substrate saturation kinetics of myo-inositol uptake analyses indicated that inhibition of inositol transport or availability were not the main reasons for the reduced biosynthesis of IPC and PI observed in tamoxifen treated parasites. An in vitro enzymatic assay was used to show that tamoxifen was able to inhibit the Leishmania IPC synthase with an IC₅₀ value of 8.48 μM (95% CI 7.68-9.37), suggesting that this enzyme is most likely one of the targets for this compound in the parasites.

SUBMITTER: Trinconi CT

PROVIDER: S-EPMC6216108 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

Trinconi Cristiana T CT Miguel Danilo C DC Silber Ariel M AM Brown Christopher C Mina John G M JGM Denny Paul W PW Heise Norton N Uliana Silvia R B SRB

International journal for parasitology. Drugs and drug resistance 20181024 3

Previous work from our group showed that tamoxifen, an oral drug that has been in use for the treatment of breast cancer for over 40 years, is active both in vitro and in vivo against several species of Leishmania, the etiological agent of leishmaniasis. Using a combination of metabolic labeling with [<sup>3</sup>H]-sphingosine and myo-[<sup>3</sup>H]-inositol, alkaline hydrolysis, HPTLC fractionations and mass spectrometry analyses, we observed a perturbation in the metabolism of inositolphosph ...[more]

PMID: 30399513

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Project description:ObjectivePlatelets, which are mainly known for their role in hemostasis, are now known to play a crucial role in metastasis. Tamoxifen is a selective estrogen receptor modulator that is widely used for the treatment of breast cancer. Tamoxifen and its metabolites have been shown to directly impact platelet function, suggesting that this drug has additional mechanisms of action. The purpose of this study was to determine whether tamoxifen exerts antitumor effects through direct platelet inhibition.Approach and resultsThis study found that pretreatment with tamoxifen leads to a significant inhibition of platelet activation. Platelets exposed to tamoxifen released significantly lower amounts of proangiogenic regulator vascular endothelial growth factor. In vitro angiogenesis assays confirmed that tamoxifen pretreatment led to diminished capillary tube formation and decreased endothelial migration. Tamoxifen and its metabolite, 4-hydroxytamoxifen, also significantly inhibited the ability of platelets to promote metastasis in vitro. Using a membrane-based array, we identified several proteins associated with angiogenesis metastasis that were lower in activated releasate from tamoxifen-treated platelets, including angiogenin, chemokine (C-X-C motif) ligand 1, chemokine (C-C motif) ligand 5, epidermal growth factor, chemokine (C-X-C motif) ligand 5, platelet-derived growth factor dimeric isoform BB, whereas antiangiogenic angiopoietin-1 was elevated. Platelets isolated from patients on tamoxifen maintenance therapy were also found to have decreased activation responses, diminished vascular endothelial growth factor release, and lower angiogenic and metastatic potential.ConclusionsWe demonstrate that tamoxifen and its metabolite 4-hydroxytamoxifen directly alter platelet function leading to decreased angiogenic and metastatic potential. Furthermore, this study supports the idea of utilizing targeted platelet therapies to inhibit the platelet's role in angiogenesis and malignancy.

Project description:Leishmaniases are a set of tropical and sub-tropical diseases caused by protozoan parasites of the genus Leishmania whose severity ranges from self-healing cutaneous lesions to fatal visceral infections. Leishmania parasites synthesise a wide array of cell surface and secreted glycoconjugates that play important roles in infection. These glycoconjugates are particularly abundant in the promastigote form and known to be essential for establishment of infection in the insect midgut and effective transmission to the mammalian host. Since they are rich in galactose, their biosynthesis requires an ample supply of UDP-galactose. This nucleotide-sugar arises from epimerisation of UDP-glucose but also from an uncharacterised galactose salvage pathway. In this study, we evaluated the role of the newly characterised UDP-sugar pyrophosphorylase (USP) of Leishmania major in UDP-galactose biosynthesis. Upon deletion of the USP encoding gene, L. major lost the ability to synthesise UDP-galactose from galactose-1-phosphate but its ability to convert glucose-1-phosphate into UDP-glucose was fully maintained. Thus USP plays a role in UDP-galactose activation but does not significantly contribute to the de novo synthesis of UDP-glucose. Accordingly, USP was shown to be dispensable for growth and glycoconjugate biosynthesis under standard growth conditions. However, in a mutant seriously impaired in the de novo synthesis of UDP-galactose (due to deficiency of the UDP-glucose pyrophosphorylase) addition of extracellular galactose increased biosynthesis of the cell surface lipophosphoglycan. Thus under restrictive conditions, such as those encountered by Leishmania in its natural habitat, galactose salvage by USP may play a substantial role in biosynthesis of the UDP-galactose pool. We hypothesise that USP recycles galactose from the blood meal within the midgut of the insect for synthesis of the promastigote glycocalyx and thereby contributes to successful vector infection.

Dataset Information

Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

Publications

Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

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