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

Abstract

Hydroxyl radical ('OH) formation by neutrophils in vitro requires exogenous iron. Two recent studies [Britigan, Rosen, Thompson, Chai & Cohen (1986) J. Biol. Chem. 261, 17026-17032;Winterbourn (1987) J. Clin. Invest. 78, 545-550] both reported that neutrophil degranulation could potentially inhibit the formation of OH, but differed in their conclusions as to the responsible factor, myeloperoxidase (MPO) or lactoferrin (LF). By using a previously developed spin-trapping system which allows specific on-line detection of superoxide anion (02-) and GOH production, the impact of MPO and LF release on neutrophil *OH production was compared. When iron-diethylenetriaminepenta-acetic acid-supplemented neutrophils were stimulated with phorbol myristate acetate or opsonized zymosan, *OH formation occurred, but terminated prematurely in spite of continued 02-generation. Inhibition of MPO by azide increased the magnitude, but not the duration, of OH formation. No azide effect was noted when MPO-deficient neutrophils were used. Anti-LF antibody increased both the magnitude and duration of 'OH generation. Pretreatment of neutrophils with cytochalasin B to prevent phagosome formation did not alter the relative impact of azide or anti-LF on neutrophil GOH production. An effect of azide or anti-LF on spin-trappedadduct stability was eliminated as a confounding factor. These data indicate that neutrophils possess two mechanisms for limiting GOH production. Implications for neutrophil-derived oxidant damage are discussed.

The target antigens of antineutrophil cytoplasmic antibodies (ANCA) induced by propylthiouracil

“…And it had been shown in experiments that anti-lactoferrin antibodies could increase both the magnitude and duration of hydroxyl radical formation [22]. Therefore, we speculated that ANCA specific to antigens, other than MPO and PR3, might also involve in the pathogenesis of AASV.…”

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

“…Previous reports have found that at least two of the granular components affect the potential for * OH formation in association with the neutrophil respiratory burst. Lactoferrin and myeloperoxidase inhibit * OH formation by iron-supplemented neutrophils by sequestering iron in a noncatalytic form and consuming H202, respectively (15,20,54). In contrast, it seemed possible that neutrophil proteases through their action on the peptide PVD could alter the potential of iron bound to PVD to participate in the Haber-Weiss reaction.…”

Biochemical basis for the killing ofCryptococcus neoformansby rat peritoneal cells

“…Since peritoneal cells (macrophages) lack MPO, the cytotoxicity of H,O~ is mainly increased by the generation of hydroxyl radical [30]. Free radical damage in biological systems is largely attributed to OH" generation [8]; however, the capacity to form hydroxyl radical in significant concentrations has recently been questioned [2]. In this report we show that hydroxyl radical is implicated in the killing of C neoJbrmans by rat PC demonstrated by the fact that killing of C neofornlans was effectively inhibited by benzoate, a reagent scavenger of hydroxyl radical (Fig.…”