An Alternative Mechanism for the Production of Hydroxyl Radicals by Stimulated Neutrophils

Abstract

The importance of oxygen in the microbiocidal activity of polymorphic leukocytes has been established¹ for many years. Twenty years ago it was shown² that the two-electron reduction product of oxygen, hydrogen peroxide, is present in the medium surrounding stimulated cells. Later, the superoxide ion, the one-electron reuction product of oxygen was also found³ to be produced by phagocytosing neutrophils. The three-electon reduction product, the hydroxyl radical, has since been found⁴ to be produced by these activated cells. A flurry of mechanisms, seeking to account for the genesis of, and relationship between, these potentially reactive species has resulted. It is now generally accepted that the superoxide ion is produced⁵ by a membrane-bound enzyme that requires NAD(P)H. It is not yet known whether the hydrogen peroxide that is found extracellularly arises by the direct two-electron reduction of oxygen or through the spontaneous disproportionation of superoxide:

$$ {O_2} + 2e + 2H + \to {H_2}{O_2}\ $$

(1)

$$ 20_{2}^{-}+2{{H}^{+}}\to {{H}_{2}}{{O}_{2}}+{{O}_{2}} $$

(2)