Abstract
The inability of the bloodstream form of Trypanosoma brucei brucei to decompose hydrogen peroxide forms the basis of our attempt to develop new pharmacological agents to kill these organisms. Approximately 1-3% of the oxygen consumed by these parasites appears in the form of hydrogen peroxide. Our previous observation that free radical initiators such as heme and hematoporphyrin D proved to be trypanocidal in vitro and in vivo, respectively, prompted this investigation into the mechanism of action of this class of compounds to enhance their therapeutic efficacy. The locus of H2O2 production within the trypanosome was examined using cell-free homogenates. Experiments described herein suggest that H2O2 is formed by the alpha-glycerol phosphate dehydrogenase in an adventitious manner, and that no enzymatic means of disposing of this potentially toxic compound are present with the organisms. Naphthoquinones were found to substantially increase the rate of both oxygen consumption and H2O2 production by trypanosomal mitochondrial preparations. Presumably, the naphthoquinones are acting as coenzyme Q analogues. The addition of sublytic concentrations of both naphthoquinones and heme leads to a synergistic lysis of the organisms in vitro. Another approach to increasing the susceptibility of T. b. brucei to free radical damage involved reduction of the intracellular concentration of glutathione. This was accomplished through the use of trypanocidal arsenicals. Melarsenoxide and heme acted synergistically in vitro, an effect which was further enhanced via addition of a naphthoquinone. Moreover, hematoporphyrin D and tryparsamide were shown to have a synergistic effect in T. b. brucei-infected mice.
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Selected References
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- BAERNSTEIN H. D. A review of electron transport mechanisms in parasitic protozoa. J Parasitol. 1963 Feb;49:12–21. [PubMed] [Google Scholar]
- Boveris A., Oshino N., Chance B. The cellular production of hydrogen peroxide. Biochem J. 1972 Jul;128(3):617–630. doi: 10.1042/bj1280617. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chang K. P., Chang C. S., Sassa S. Heme biosynthesis in bacterium-protozoon symbioses: enzymic defects in host hemoflagellates and complemental role of their intracellular symbiotes. Proc Natl Acad Sci U S A. 1975 Aug;72(8):2979–2983. doi: 10.1073/pnas.72.8.2979. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dawson A. P., Thorne C. J. L-3-glycerophosphate dehydrogenase from pig brain mitochondria. Methods Enzymol. 1975;41:254–259. doi: 10.1016/s0076-6879(75)41058-8. [DOI] [PubMed] [Google Scholar]
- FULTON J. D., SPOONER D. F. Inhibition of the respiration of Trypanosoma rhodesiense by thiols. Biochem J. 1956 Jul;63(3):475–481. doi: 10.1042/bj0630475. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GRANT P. T., FULTON J. D. The catabolism of glucose by strains of Trypanosoma rhodesiense. Biochem J. 1957 Jun;66(2):242–250. doi: 10.1042/bj0660242. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GRANT P. T., SARGENT J. R. Properties of L-alpha-glycerophosphate oxidase and its role in the respiration of Trypanosoma rhodesiense. Biochem J. 1960 Aug;76:229–237. doi: 10.1042/bj0760229. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Homan-Müller J. W., Weening R. S., Roos D. Production of hydrogen peroxide by phagocytizing human granulocytes. J Lab Clin Med. 1975 Feb;85(2):198–207. [PubMed] [Google Scholar]
- Kusel J. P., Boveris A., Storey B. T. H2O2 production and cytochrome c peroxidase activity in mitochondria isolated from the trypanosomatid hemoflagellate Crithidia fasciculata. Arch Biochem Biophys. 1973 Oct;158(2):799–805. doi: 10.1016/0003-9861(73)90574-2. [DOI] [PubMed] [Google Scholar]
- LIPSON R. L., BALDES E. J., OLSEN A. M. The use of a derivative of hematoporhyrin in tumor detection. J Natl Cancer Inst. 1961 Jan;26:1–11. [PubMed] [Google Scholar]
- Lanham S. M., Godfrey D. G. Isolation of salivarian trypanosomes from man and other mammals using DEAE-cellulose. Exp Parasitol. 1970 Dec;28(3):521–534. doi: 10.1016/0014-4894(70)90120-7. [DOI] [PubMed] [Google Scholar]
- Meshnick S. R., Chang K. P., Cerami A. Heme lysis of the bloodstream forms of Trypanosoma brucei. Biochem Pharmacol. 1977 Oct 15;26(20):1923–1928. doi: 10.1016/0006-2952(77)90167-8. [DOI] [PubMed] [Google Scholar]
- Opperdoes F. R., Borst P., Bakker S., Leene W. Localization of glycerol-3-phosphate oxidase in the mitochondrion and particulate NAD+-linked glycerol-3-phosphate dehydrogenase in the microbodies of the bloodstream form to Trypanosoma brucei. Eur J Biochem. 1977 Jun 1;76(1):29–39. doi: 10.1111/j.1432-1033.1977.tb11567.x. [DOI] [PubMed] [Google Scholar]
- Opperdoes F. R., Borst P., Spits H. Particle-bound enzymes in the bloodstream form of Trypanosoma brucei. Eur J Biochem. 1977 Jun 1;76(1):21–28. doi: 10.1111/j.1432-1033.1977.tb11566.x. [DOI] [PubMed] [Google Scholar]
- Tietze F. Enzymic method for quantitative determination of nanogram amounts of total and oxidized glutathione: applications to mammalian blood and other tissues. Anal Biochem. 1969 Mar;27(3):502–522. doi: 10.1016/0003-2697(69)90064-5. [DOI] [PubMed] [Google Scholar]
- WILSON S. G., MORRIS K. R., LEWIS I. J., KROG E. The effects of trypanosomiasis on rural economy with special reference to the Sudan, Bechuanaland and West Africa. Bull World Health Organ. 1963;28(5-6):595–613. [PMC free article] [PubMed] [Google Scholar]
- Williamson J. Chemotherapy of African trypanosomiasis. Trans R Soc Trop Med Hyg. 1976;70(2):117–119. doi: 10.1016/0035-9203(76)90166-8. [DOI] [PubMed] [Google Scholar]