Reactive oxygen species and airway inflammation

As a highly reactive substance produced in biological systems by the one-electron reduction of oxygen, superoxide (O(2) (-)) seemed a likely candidate as a bactericidal agent in leukocytes. The reduction of cytochrome c, a process in which O(2) (-) may serve as an electron donor, was found to occur when the cytochrome was incubated with leukocytes. O(2) (-) was identified as the agent responsible for the leukocyte-mediated reduction of cytochrome c by the demonstration that the reaction was abolished by superoxide dismutase, an enzyme that destroys O(2) (-), but not by boiled dismutase, albumin, or catalase. Leukocyte O(2) (-) production doubled in the presence of latex particles. The average rate of formation of O(2) (-) in the presence of these particles was 1.03 nmol/10(7) cells per 15 min. This rate, however, is only a lower limit of the true rate of O(2) (-) production, since any O(2) (-) which reacted with constituents other than cytochrome c would have gone undetected. Thus. O(2) (-) is made by leukocytes under circumstances which suggest that it may be involved in bacterial killing.

Radicals in the gas phase of both mainstream and sidestream cigarette smoke have been studied using electron-spin resonance ESR spin-trapping techniques with alpha-phenyl-N-tert-butyl nitrone (PBN) as the spin trap. The principal radicals we trap appear to be alkoxyl radicals. Mainstream and sidestream gas-phase smoke each have about the same concentration of radicals, about 1 X 10(16) radicals per cigarette (or 5 X 10(14) per puff). These radicals are reactive, yet they appear to be remarkably long-lived: they are still spin trapped from gas-phase smoke after more than 5 min. We propose that a steady-state concentration of reactive radicals exists in gas phase cigarette smoke. We suggest that this steady state is produced by the slow oxidation of nitric oxide (present in high concentrations in smoke and relatively unreactive) to the more reactive nitrogen dioxide, followed by the reaction of nitrogen dioxide with reactive organic molecules in smoke (such as olefins and dienes). Preliminary experiments reported here support this hypothesis. Tar from both mainstream and sidestream smoke contains persistent free radicals that exhibit broad, single-line ESR spectra with g values of 2.003. The tar radical can be extracted into tert-butylbenzene and other organic solvents, and we have applied a variety of fractionation procedures to these solutions. Most of the radicals occur in the fractions that contain the phenolic tobacco leaf pigments. Treatment of alcoholic solutions of tar with base generates a new group of radicals that appear to be semiquinone radicals derived from the oxidation of the phenolic and polyphenolic species in tar.