Production of hydroxyl radical by human alveolar macrophages.

Stimulated human alveolar macrophages were demonstrated to oxidize B-methyl proprionaldehyde (methional) or 2-keto-4-thiomethylbutyric acid to ethylene (C2H4). Agents which are believed to scavenge the hydroxyl radical (.OH), sodium benzoate, and mannitol, as well as scavengers of superoxide anion (O2-) or hydrogen peroxide, decreased C2H4 production, implicaing .OH as the oxidizing radical. Differences in C2H4 rpoduction, as well as oxygen uptake and O2- release between human alveolar macrophages and polymorphonuclear leukocytes, were also documented.

Comparison of the metabolism of alveolar macrophages from humans, rats, and rabbits: phorbol myristate acetate.

Metabolic activities of unstimulated or stimulated AMs from humans, rats, and rabbits were examined and compared in vitro. Rates of oxygen consumption, chemiluminescence, and glucose (1- or 6-14C) oxidation by unstimulated AMs from these three species increased following stimulation of the AMs by bacteria or PMA. Although the absolute metabolic responses of AMs from humans, rats, or wild rabbits were different, the metabolic activities from each species were nearly identical when compared on the basis of protein content of the cells. In contrast to the enhanced biochemical responses of AMs from humans, rats, or wild rabbits, stimulated AMs from certain commercially supplied rabbits failed to increase their metabolism. The failure of AMs from these rabbits to respond metabolically was probably due to an acquired abnormality resulting from their care and storage at the supplier. The defect was associated with the presence of large numbers of Bordetella bronchiseptica organisms in the lavage effluents from these commercially supplied rabbits. This abnormality in metabolism of AMs was reversed following prolonged residence of the rabbits in the laboratory, and the correction of the defect was accompanied by a disappearance of B. bronchiseptica from the lavage fluid. The results comprehensively compare and contrast the metabolism of AMs from humans and animals and emphasize the need to document the appropriateness of animal models before using them to predict biologic reactions of humans.

The effect of phorbol myristate acetate on the metabolism and ultrastructure of human alveolar macrophages.

In the present investigation we examined the influence of the surface-active agent phorbol myristate acetate (PMA) and opsonized heat-killed bacteria (HKB) on oxygen consumption, superoxide release, and glucose oxidation of human alveolar macrophages (AM). Both PMA and HKB produced a surge in oxygen consumption, superoxide release, and oxidation of 1-14C-glucose and 6-14C-glucose by human AM. Examination of AM by electron microscopy following stimulation by these two agents demonstrated membrane ruffling, loss of microvilli, and increased vacuolization in PMA-treated cells and phagocytic vacuoles containing bacteria in HKB-treated cells. The vacuolization produced by PMA-treated AM was much less striking than the vacuolization produced in PMA-treated leukocytes. The similarity in the metabolic and some of the physical responses of AM stimulated by PMA and HKB suggest that PMA may be a useful agent for evaluating cell-membrane-related events of phagocytosis in AM.

Inhibition of human neutrophil oxidative metabolism and degranulation in vitro by nitroblue tetrazolium and vitamin E.

The effect of a mixture of nitroblue tetrazolium (NBT) and vitamin E on the metabolism and ultrastructure of polymorphonuclear leukocytes (PMN) from normal subjects or patients with chronic granulomatous disease (CGD) was determined in vitro. Increasing concentrations of NBT and vitamin E progressively decreased rates of oxygen consumption and 1-14C-glucose oxidation by normal PMN stimulated with particulates to a degree that exceeded either agent alone. NBT-vitamin-E also inhibited vacuole formation and the cytochemical release of myeloperoxidase-positive granules. The depressed oxidative metabolism and degranulation of NBT-vitamin-E-treated control PMN closely approximated the blunted responses of CGD PMN which were similar alone or in the presence of NBT-vitamin-E. In contrast to these effects, the highest concentration of NBT-vitamin-E used in the study did not damage, decrease rates of unstimulated oxidative metabolism of, or impair ingestion of particulates by control or CGD PMN. NBT and vitamin E impose a state on normal PMN which is remarkably similar to that observed in PMN from patients with CGD.

Chemiluminescence by human alveolar macrophages: stimulation with heat-killed bacteria or phorobol myristate acetate.

Chemiluminescence of human alveolar macrophages (AM) was evaluated in vitro. Unstimulated AM generated chemiluminescence that remained constant during incubation. Addition of heat-killed Staphylococcus aureus 502A (HKB) or a chemical agent, phorbol myristate acetate, produced high rates of chemiluminescence that were significantly (P less than 0.05) increased over unstimulated AM. Phorbol myristate acetate-and HKB-stimulated increases in AM chemiluminescence were completely blocked by the enzyme superoxide dismutase. In comparison with unstimulated polymorphonuclear leukocytes, unstimulated AM had significantly (P less than 0.005) greater levels of chemiluminescence. However, after stimulation by phorbol myristate acetate or HKB, AM showed less chemiluminescence than similarly treated polymorphonuclear leukocytes.