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On the pro‐oxidant effects of haemozoin
Author(s) -
Oliveira Marcus F,
Timm Bruno L,
Machado Ednildo A,
Miranda Kildare,
Attias Márcia,
Silva José R,
Dansa-Petretski Marı́lvia,
de Oliveira Marco A,
de Souza Wanderley,
Pinhal Nelson M,
Sousa João J.F,
Vugman Ney V,
Oliveira Pedro L
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02243-3
Subject(s) - tbars , chemistry , electron paramagnetic resonance , deoxyribose , liposome , lipid peroxidation , radical , substrate (aquarium) , thiobarbituric acid , biochemistry , biophysics , photochemistry , oxidative stress , nuclear magnetic resonance , biology , dna , ecology , physics
Haemozoin (Hz) is a haem aggregate produced in some blood‐feeding organisms. There is a general belief that Hz formation would be a protective mechanism against haem toxicity. Here we show that when aggregated into Hz, haem is less deleterious than its free form. When haem was added to phosphatidylcholine (PC) liposomes, there was an intense stimulation of oxygen consumption, which did not occur when Hz was incubated with the same preparation. Evaluation of oxygen radical attack to lipids, by measurement of thiobarbituric acid reactive substances (TBARS), showed significantly lower levels of lipid peroxidation in samples containing PC liposomes incubated with Hz than with haem. However, TBARS production induced by Hz was much higher when using 2‐deoxyribose (2‐DR) as substrate, than with PC liposomes. Spin‐trapping analysis by electron paramagnetic resonance (EPR) of Hz and tert ‐butylhydroperoxide ( tert ‐BuOOH) showed that production of methoxyl and tert ‐butoxyl radicals was only slightly reduced compared to what was observed with haem. Interestingly, when large Hz crystals were used in 2‐DR TBARS assays and tert ‐BuOOH EPR experiments, the pro‐oxidant effects of Hz were strongly reduced. Moreover, increasing concentrations of Hz did not induce erythrocyte lysis, as occurred with haem. Thus, the reduced capacity of Hz to impose radical damage seems to result from steric hindrance of substrates to access the aggregated haem, that becomes less available to participate in redox reactions.