Which of the following statements are true of oxidants?

A. In addition to their pathophysiologic roles in inflammation, injury, and infection, oxidants also have physiologic roles.

B. Oxidants may be generated from activated neutrophils and during reperfusion following a period of ischemia.

C. The deleterious effects of oxidants include lipid peroxidation and cell membrane damage, oxidative damage to DNA, and inhibition of adenosine triphosphate (ATP) synthesis.

D. The mechanism of ischemia-reperfusion injury involved the catalytic production of superoxide anion (O 2•) by the enzyme xanthine oxidase.

DISCUSSION: Oxidants are reactive oxygen metabolites that have both physiologic and pathophysiologic roles. As potent oxidizing agents, oxidants are involved in cytochrome P 450–mediated oxidations, for example. In pathophysiologic processes associated with inflammation, injury, and infection, oxidants may be generated by activated neutrophils and in ischemia-reperfusion injury. During ischemia, the enzyme xanthine oxidase accumulates. When oxygen availability increases during reperfusion, O 2• is formed in a reaction catalyzed by xanthine oxidase. Further oxidant formation ensues, causing the production of H 2O 2 and the extremely reactive hydroxyl ion (OH•). Oxidants may cause direct cell damage by the mechanisms of lipid peroxidation and cell membrane disruption, inhibition of ATP synthesis, reduction of cellular nicotinamide adenine dinucleotide (NAD), and oxidative damage to DNA and amino acids. In addition, oxidants may have a chemotactic role, leading to leukocyte infiltration and activation, causing further tissue damage by the release of cytotoxic proteases.