Anne Johansson

Alveolar macrophages in rabbits exposed to nickel dust. Ultrastructural changes and effect on phagocytosis.

Abstract Two groups of four rabbits each were exposed to 0.5 and 2.0 mg/m 3 of metallic nickel dust respectively, for 4 weeks (5 days/week, 6 hours/day). About half of the particle masses penetrated a Casella preseparator. After exposure the lungs were extracted and lavaged. Compared to four control rabbits significant effects were seen in both exposed groups with regard to lung weight and density as well as phagocytic activity, size distribution, and ultrastructure of the alveolar macrophages (numerous slender microvilli and long protrusions from the cell surface and laminated structures similar to those seen in alveolar type II cells). The effects on the macrophages were probably not caused directly by nickel. The lung washing from the exposed rabbits contained an amorphous substance rich in phospholipids and laminated structures. Apart from the ultrastructural changes the effects seemed to be dose related. The results of exposure to metallic nickel dust have at least some features in common with “alveolar lipoproteinosis,” described in rats exposed to silica dust, and with “pulmonary alveolar proteinosis,” described in man.

Effects of long-term nickel dust exposure on rabbit alveolar epithelium

Abstract Lungs from rabbits exposed to 1 mg/m3 metallic nickel dust for 3 and 6 months, 5 days/week, 6 hr/day, were examined by light and electron microscopy. Morphometric measurements showed threefold and twofold increases in volume density of alveolar type II cells after 3 and 6 months, respectively. The type II cells were extremely large, especially in the 3-month-exposed rabbits, and contained large amounts of lamellar bodies. Alveoli were rich in large, foamy macrophages and a granular material which previously has been found to consist mainly of phospholipid. This material probably represents an overproduction of surfactant by the type II cells. The 6-month-exposed rabbits had foci of pneumonia, suggesting a higher susceptibility to pulmonary infections, possibly due to a decreased function of alveolar macrophages.

Effects of nickel dust on rabbit alveolar epithelium

Abstract Eight male rabbits were exposed to metallic nickel dust, during 1 month (5 days/week, 6 hr/day) at a concentration of 1.7 mg/m 3 (SD 0.5), about 40% of which was respirable. Morphometric measurements on the lungs of exposed rabbits showed about a twofold increase in volume density of type II alveolar epithelial cells compared to eight controls. This increment was about the same as the average increase in phospholipids in the lung parenchyma of the rabbits described elsewhere. The volume density of lamellar bodies within the cytoplasm of the type II cell was not significantly increased. Large amounts of laminated structures, resembling those in the alveolar type II cells, were also found free in the alveoli in the exposed rabbits.

Rabbit lung after inhalation of soluble nickel: II. Effects on lung tissue and phospholipids

Rabbits were exposed to soluble nickel chloride, about 0.3 mg/m3 as nickel, for about 1 month (5 days/week, 6 hr/day). The upper lobe in the left lung was examined with light microscopy and samples from the left lower lobe with electron microscopy. Nodular accumulation of macrophages and laminated structures occurred in alveoli of all exposed rabbits, but otherwise no inflammatory reactions. Volume density of the alveolar epithelial type II cells was doubled due to increased cell number as well as cell volume. The tissue content of phospholipids, determined in the lower lobe of the left lung, had increased by about 40%, mainly due to elevated disaturated phosphatidylcholines. The effect pattern was almost identical to that seen earlier in inhalation experiments with metallic nickel dust, strongly indicating that nickel ions are responsible also for the changes seen after exposure to metallic nickel. This suggests that all nickel compounds may produce the pathological condition, which is similar to that seen in the disease pulmonary alveolar proteinosis.

Rabbit lung after inhalation of hexa- and trivalent chromium.

Rabbits were exposed to aerosols of hexavalent (Na2CrO4) and trivalent chromium (Cr(NO3)3) at concentrations of 0.9 and 0.6 mg/m3 of chromium respectively for 4-6 weeks (5 days/week and 6 hr/day). Three of eight rabbits exposed to Cr(VI) and three of eight rabbits exposed to Cr(III) showed nodular accumulations of alveolar macrophages, similar to the lesions observed in previous experiments after exposure to Ni2+, Cd2+, or metallic nickel. Macrophages from rabbits exposed to Cr(III) usually contained round dark inclusions, large lysosomes, and laminated inclusions similar to the lamellar bodies in the type II cells, and most macrophages from rabbits exposed to Cr(VI) showed enlarged lysosomes. However, the total amount of phospholipids and the volume density of type II cells did not differ significantly between exposed rabbits and controls. Our findings indicate that the macrophages are directly affected by chromium. The accumulation of laminated structures in the alveolar macrophages after Cr(III) exposure might be due to an impaired catabolism of surfactant.

Rabbit alveolar macrophages after inhalation of soluble cadmium, cobalt, and copper: a comparison with the effects of soluble nickel.

Rabbits were exposed to aerosols of chlorides of cadmium, copper, and cobalt (0.4-0.6 mg/m3 as metal) for 1 month (5 days/weeks and 6 hr/day). The effects of alveolar macrophages were compared with earlier reported effects of nickel chloride (0.3 mg/m3 as Ni). Effects of Cd2+ exposure resembled those of Ni2+ exposure. The number of macrophages in lavage fluid and the variance of cell diameters were thus increased and many cells contained lamellated inclusions. Contrary to macrophages from Ni2+-exposed rabbits, the surface of about 50% of the cells had cytoplasmic blebs. However, such cells were rarely seen by scanning electron microscopy. There were significantly more polymorphonucleated neutrophils and small lymphocytes, suggesting lung parenchymal damage. Cells from Cd2+-exposed animals, like cells from Ni2+-exposed ones, showed an increased oxidative metabolic activity after stimulation with Escherichia coli bacteria. Bactericidal capacity, on the other hand, tended to be enhanced rather than decreased, as in the nickel experiment. After CO2+ exposure, the number of macrophages was slightly increased in the lavage fluid and the cells showed an increased metabolic activity both at rest and upon stimulation with bacteria. Cu2+ exposure gave a slight increase in lamellated inclusions in the macrophages.

Rabbit alveolar macrophages after inhalation of hexa- and trivalent chromium

Rabbits inhaled aerosols of hexavalent chromium (Na2CrO4) and trivalent chromium (Cr(NO3)3) at concentrations of 0.9 and 0.6 mg/m3 of the metal, respectively, for 4-6 weeks (5 days/week and 6 hr/day). Significantly more macrophages were obtained from the lungs of rabbits exposed to Cr(VI) but not from rabbits exposed to Cr(III) as compared with the controls. Macrophages from rabbits exposed to Cr(III) showed several conspicuous changes. About one-third of the macrophages contained round dark inclusions, 0.5-1.5 micron diameter, rich in chromium. Most cells had very large lysosomes which contained membranous fragments of different sizes surrounded by a more homogeneous matrix. Laminated inclusions similar to the lamellar bodies in the type II cells increased in number as did the percentage of cells with a smooth cell surface. Also macrophages from rabbits exposed to Cr(VI) showed morphological changes. The most pronounced one was enlarged lysosomes which contained short lamellae and electron-dense patchy inclusions. Only Cr(III) produced functional changes of the macrophages. The metabolic activity measured by reduction of nitroblue tetrazolium was increased and the phagocytic activity reduced.

Morphology and function of alveolar macrophages after long-term nickel exposure

Abstract In a group of 24 rabbits, 12 were exposed to 1.0 mg/m 3 (SD 0.7) of metallic nickel dust and 12 used as controls. Six rabbits were exposed for 3 months and six for 6 months (5 days/week, 6 hr/day). After exposure the lungs were extracted and lavaged. Macrophages were examined by light and electron microscopy and their oxidative metabolism studied by measuring the reduction of nitroblue tetrazolium. Most macrophages had a strikingly smooth surface and a cytoplasm containing closely packed, membrane-bound lamellar bodies. The proportion of this cell type was significantly larger after 6 months than after 3 months exposure. These macrophages differed not only from those of controls but also from macrophages in rabbits earlier exposed for 1 month to about the same concentration of metallic nickel dust. Macrophages from these rabbits had an active cell surface with numerous slender microvilli and long protrusions. The metabolism was significantly higher than in controls after both 3 and 6 months exposure. In contrast to macrophages from the 1-month experiment and controls, these macrophages did not significantly increase their metabolism upon stimulation with bacteria.

Morphology and release of lysozyme following exposure of rabbit lung macrophages to nickel or cadmium in vitro

Lung macrophages lavaged from 7 rabbits were incubated with 0, 3, 6, 12 and 24 micrograms/ml of nickel as NiCl2 and macrophages from 4 rabbits were incubated with 0, 0.1, 1, 3 and 6 micrograms/ml of cadmium as CdCl2. After 2 days lysozyme activity in the medium in which the macrophages were cultivated, was estimated using a technique with agar plates prepared with heat-killed Micrococcus lysodeikticus. Macrophage morphology was examined by scanning and transmission electron microscopy. For nickel there was a dose-related inverse relationship between the lysozyme activity and concentration of nickel. Many macrophages exposed to the higher nickel concentrations had a rounded form and, thus, the surface area of each cell which came in contact with the glass appeared to be less than that for control macrophages. There was, however, no increase in the number of macrophages detached from their glass support. Cadmium exposure did not influence lysozyme levels of activity, in spite of morphological indications of cell toxicity. From the present study we conclude that the decreased lysozyme activity seen previously in vivo after nickel inhalation is likely to be due to a direct effect of nickel ions on macrophages and that the increased lysozyme activity seen in vivo after cadmium inhalation is probably a secondary effect, subsequent to inflammation.

Alveolar macrophage abnormalities in rabbits exposed to low concentrations of trivalent chromium

Rabbits were exposed by inhalation to a trivalent chromium compound (Cr(NO3)3) at a mean chromium concentration of 0.6 or 2.3 mg/m3 for about 4 months, 5 days/week and 6 hr/day. Light microscopic examination of the lungs revealed that both chromium levels induced a nodular intraalveolar accumulation of enlarged macrophages with granular, eosinophilic cytoplasm. Some macrophages were multinucleated and some showed advanced degenerative changes with disruption of cellular borders and nuclear pyknosis. The changes were most prominent in rabbits exposed to the high concentration and were in some areas associated with a mild interstitial infiltration of lymphocytes, neutrophils, and eosinophils. Electron microscopic examination of macrophages lavaged from the lungs revealed numerous enlarged lysosomes with membranous structures, distinct rounded inclusions, which by X-ray microanalysis were found to contain high amounts of chromium, and increased numbers of laminated inclusions probably representing ingested surfactant. The number of macrophages with a smooth surface was significantly increased. The macrophages in the lung tissue showed the same changes and in addition nodules of multinucleated giant cells were found. Morphometric estimation of the volume density of the type II cells did not reveal any significant differences between controls and rabbits exposed to the high concentration of chromium. In spite of the elevated number of laminated structures in the macrophages the amounts of phosphatidylcholine and 1,2-dipalmitoylphosphatidylcholine were not significantly increased in the lung. This indicates a reduced catabolism of surfactant by the alveolar macrophages.