Role of free radical processes in stimulated human polymorphonuclear leukocytes

Abstract

Human polymorphonuclear leukocytes produce large quantities of superoxide when they attack and kill bacteria. However, superoxide is a weak oxidizing and reducing agent, and other more reactive oxygen species derived from reactions of superoxide are suggested to participate in the killing processes. To test the hypothesis that a reactive free radical or singlet oxygen is involved in bactericidal activity, human polymorphonuclear leukocytes were exposed to phagocytozable particles containing lipids that contain the easily autoxidized 1,4-diene moiety. After incubation the preparations were extracted and the extracts reduced with NaBH4 to convert hydroperoxides to stable alcohols. Using gas chromatography/mass spectrometry to analyze the extracts, we were unable to detect products unless iron salts were added to the medium. The products obtained by extraction are those that would be expected if both free radical chain autoxidation and 1O2 oxidation were taking place. In summary, we find that polymorphonuclear leukocytes do not cause peroxidation, implying that formation of strongly oxidizing free radicals is not an intrinsic property of the leukocyte. Added iron catalyzes peroxidation by activated leukocytes yielding an unusual distribution of hydroxylated products.

DNA damage by oxygen‐derived species Its mechanism and measurement in mammalian systems

“…neutraphils do not them&es appear to can. tain nny form of metnl ion cntalyse that will convert HaOr into 'OH [47][48][49]'. Oxidative stress [XJ-541 and DNA dnmagc [51 J also occur when some mammzGtln cclis are exposed to tumor necrosis factor.…”

Possible role of bacterial siderophores in inflammation. Iron bound to the Pseudomonas siderophore pyochelin can function as a hydroxyl radical catalyst.

“…Although it has been reported that neutrophils have the endogenous capacity for *OH formation (8)(9)(10)(11)(12)(13), the experimental techniques used in these studies have been criticized for a lack of specificity (14). Recent studies using spin trapping and other techniques have strongly suggested that an exogenous transition metal catalyst must be present for neutrophil activation to result in -OH generation (3,(15)(16)(17)(18)(19)(20).…”

Neutrophil degranulation inhibits potential hydroxyl-radical formation. Relative impact of myeloperoxidase and lactoferrin release on hydroxyl-radical production by iron-supplemented neutrophils assessed by spin-trapping techniques

“…Recent work in several laboratories has forced re-evaluation of original assumptions regarding the endogenous capacity of neutrophils to generate GOH [25][26][27][28][29][30][31][32][33][34]. Studies employing m.s.…”

“…Studies employing m.s. [32,33], deoxyribose oxidation ( [30,31]; B. E. Britigan, unpublished work), phenylalanine hydroxylation [34], and spin trapping [25][26][27][28][29] have failed to detect production of 'OH by neutrophils unless iron salts and a chelating-agent were included in the system. These studies suggest that generation of *OH in vivo in association with neutrophil stimulation requires the presence of an exogenous catalyst.…”