Phospholipase A 2 from Trypanosoma brucei gambiense and Trypanosoma brucei brucei : Inhibition by Organotins
ABSTRACT Activity and kinetics of phospholipase A2 (PLA2) from Trypanosoma brucei gambiense (Wellcome strain) and Trypanosoma brucei brucei (GUTat 3.1) were examined using two different fluorescent substrates. The activity in the supernatants of sonicated parasites was Ca2+-independent, strongly stimulated by Triton X-100 with optimum activity at 37 degrees C and pH 6.5-8.5. To encourage a possible interaction between the parasite enzyme and organotin compounds, fatty acid derivatives of dibutyltin dichloride were synthesized and evaluated as potential inhibitors of PLA2. The enzyme from the two-trypanosome species differ with respect to kinetic parameters and are noncompetitively inhibited by the organotin compounds. The Michaelis constant (KM) for PLA2 from T. b. brucei is 63.87 and 30.90 microM while for T. b. gambiense it is 119.64 and 32.91 microM for the substrates 1,2-bis-(1-pyrenebutanoyl)-sn-glycero-3-phosphocholine (PBGPC) and 2-(12-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl-1-hexadecanoyl-sn-glycero-3-phosphocholine (NBDC12-HPC), respectively.
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ABSTRACT: Oxylipins are oxygenated metabolites of fatty acids. Eicosanoids are a subset of oxylipins and include the prostaglandins and leukotrienes, which are potent regulators of host immune responses. Host cells are one source of eicosanoids and oxylipins during infection; however, another potential source of eicosanoids is the pathogen itself. A broad range of pathogenic fungi, protozoa, and helminths produce eicosanoids and other oxylipins by novel synthesis pathways. Why do these organisms produce oxylipins? Accumulating data suggest that phase change and differentiation in these organisms are controlled by oxylipins, including prostaglandins and lipoxygenase products. The precise role of pathogen-derived eicosanoids in pathogenesis remains to be determined, but the potential link between pathogen eicosanoids and the development of TH2 responses in the host is intriguing. Mammalian prostaglandins and leukotrienes have been studied extensively, and these molecules can modulate Th1 versus Th2 immune responses, chemokine production, phagocytosis, lymphocyte proliferation, and leukocyte chemotaxis. Thus, eicosanoids and oxylipins (host or microbe) may be mediators of a direct host-pathogen "cross-talk" that promotes chronic infection and hypersensitivity disease, common features of infection by eukaryotic pathogens.Clinical Microbiology Reviews 08/2003; 16(3):517-33. DOI:10.1128/CMR.16.3.517-533.2003 · 16.00 Impact Factor
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ABSTRACT: Searching for new compounds against pathogenic trypanosomes has been substantially accelerated by the development of in vitro screening assays. In an attempt to explore the chemotherapeutic potential of organotin compounds and to broaden the search for newer trypanocides, fatty acid derivatives of dibutyltin dichloride were synthesized and their in vitro trypanocidal profiles studied on Trypanosoma brucei brucei, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. A 24-h time course experiment was conducted with various concentrations of the compounds using a 24-well microtiter plate technique. The compounds tested were trypanocidal in a dose-dependent fashion: inhibiting survival and growth, resulting in irreversible morphological deformation and the eventual death of the parasites. The minimum inhibitory concentrations of the tested diorganotins are at low micromolar ranges: from 0.15-0.75 microM for T. b. brucei, T. b. gambiense and T. b. rhodesiense. These observations suggest that organotin has chemotherapeutic potential.Parasitology Research 10/2003; 91(1):5-11. DOI:10.1007/s00436-003-0861-2 · 2.33 Impact Factor