Superoxide Dismutases and the Oxidative Burst in Human Blood Polymorphonuclear Leukocytes

Abstract

Both cyanide (CN)-sensitive and CN-resistant superoxide dismutases (SOD) have been identified in human polymorphonuclear leukocytes (PMN), and located in the cytosol and granules of these cells ^1–4. These enzymes catalyse the dismutation of superoxide anion (${{O}^{-}}_{{\dot{2}}}$) to hydrogen peroxide (H₂O₂), and are thus thought to be protective in PMN against the highly reactive ${{O}^{-}}_{{\dot{2}}}$, as they are in other tissues and cells of aerobic organisms^2,4–6 However, the functional activity of PMN, i.e. their microbial killing activity, depends largely on the ability of PMN to generate ${{O}^{-}}_{{\dot{2}}}$ during their stimulated oxidative burst⁷(OB).Moreover, the OB of the PMN not only kills the ingested bacteria, but is also a suicidal event for the PMN, suggesting that the SOD might lose their activity during the OB. On the other hand it is well known that SOD activity inhibits O₂-uptake, NAD(P)H oxidation, and ${{O}^{-}}_{{\dot{2}}}$ formation by isolated subcellular fractions from PMN^8–10.