title: Probing the molecular mechanism of hypericin-induced parasite death provides insight into the role of spermidine beyond redox metabolism in Leishmania donovani.
abstract: Hypericin, a natural compound from Hypericum perforatum (St. John's wort), has been identified as a specific inhibitor of Leishmania donovani spermidine synthase (LdSS) using integrated computational and biochemical approaches. Hypericin showed in vitro inhibition of recombinant LdSS enzyme activity. The in vivo estimation of spermidine levels in Leishmania promastigotes after hypericin treatment showed significant decreases in the spermidine pools of the parasites, indicating target specificity of the inhibitor molecule. The inhibitor, hypericin, showed significant antileishmanial activity, and the mode of death showed necrosis-like features. Further, decreased trypanothione levels and increased glutathione levels with elevated reactive oxygen species (ROS) levels were observed after hypericin treatment. Supplementation with trypanothione in the medium with hypericin treatment restored in vivo trypanothione levels and ROS levels but could not prevent necrosis-like death of the parasites. However, supplementation with spermidine in the medium with hypericin treatment restored in vivo spermidine levels and parasite death was prevented to a large extent. The data overall suggest that the parasite death due to spermidine starvation as a result of LdSS inhibition is not related to elevated levels of reactive oxygen species. This suggests the involvement of spermidine in processes other than redox metabolism in Leishmania parasites. Moreover, the work provides a novel scaffold, i.e., hypericin, as a potent antileishmanial molecule.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, India.
authors.forename: Shalini
authors.initials: S
authors.lastname: Singh
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, India.
authors.forename: Shyamali
authors.initials: S
authors.lastname: Sarma
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India.
authors.forename: Shashank P
authors.initials: SP
authors.lastname: Katiyar
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, India.
authors.forename: Mousumi
authors.initials: M
authors.lastname: Das
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, India.
authors.forename: Ruchika
authors.initials: R
authors.lastname: Bhardwaj
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India.
authors.forename: Durai
authors.initials: D
authors.lastname: Sundar
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, India vdubey@iitg.ernet.in.
authors.forename: Vikash Kumar
authors.initials: VK
authors.lastname: Dubey
mesh_terms: D000818:Animals; D000873:Anthracenes; D000981:Antiprotozoal Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D007893:Leishmania donovani / Q000187:drug effects* / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects; D010084:Oxidation-Reduction; D010569:Perylene / Q000031:analogs & derivatives* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013095:Spermidine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D011436:Spermidine Synthase / Q000037:antagonists & inhibitors*
chemical_list: D000873:Anthracenes; D000981:Antiprotozoal Agents; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D010569:Perylene; C004965:hypericin; C044809:trypanothione; D011436:Spermidine Synthase; D005978:Glutathione; D013095:Spermidine