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Phagolysosomal pH and dissolution of cobalt oxide particles by alveolar macrophages
M Lundborg1, R Falk, A Johansson
1Section of Lung Medicine, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
Abstract:
We studied phagolysosomal pH in rabbit alveolar macrophages (AM) incubated with 0-15 microM chloroquine. There was a dose-related increase in pH with chloroquine concentration. Electron microscopy showed that chloroquine increased lysosomal size. In a second experiment we studied dissolution of radiolabeled cobalt oxide particles by rabbit AM, phagolysosomal pH, and lysosomal size. The cells were incubated for 2 days with 0, 2.5, and 10 microM chloroquine. Size and pH increased with chloroquine concentration. Dissolution of cobalt particles by the AM did not clearly change with pH. In a third experiment, dissolution of cobalt oxide particles in 0.1 M acetate buffer in saline with pH 4.0, 5.0, and 6.0 was studied. At the same pH, dissolution in acetate buffer was faster than in the AM, and the dissolution appeared to decrease faster with increasing pH than in the AM. A simple model for dissolution of a particle in a phagolysosome was proposed. This model predicts the types of differences in dissolution between AM and buffered saline.
Insights
Chloroquine increases the pH and size of phagolysosomes in rabbit alveolar macrophages (AM). However, this change in phagolysosomal pH did not significantly affect cobalt oxide particle dissolution by AM.
Area of Science:
- Cell Biology
- Toxicology
- Biochemistry
Background:
- Phagolysosomal pH is crucial for cellular processes.
- Understanding particle dissolution in macrophages is important for toxicology.
- Chloroquine is known to alter lysosomal function.
Purpose of the Study:
- To investigate the effect of chloroquine on phagolysosomal pH and size in rabbit alveolar macrophages (AM).
- To determine the impact of chloroquine-induced changes on the dissolution of cobalt oxide particles by AM.
- To compare particle dissolution in AM with dissolution in buffered saline.
Main Methods:
- Incubation of rabbit AM with varying concentrations of chloroquine.
- Measurement of phagolysosomal pH using established methods.
- Assessment of lysosomal size via electron microscopy.
- Quantification of radiolabeled cobalt oxide particle dissolution.
- In vitro dissolution studies in acetate buffer at different pH levels.
Main Results:
- Chloroquine caused a dose-dependent increase in phagolysosomal pH and lysosomal size in AM.
- Increased phagolysosomal pH and size did not correlate with enhanced dissolution of cobalt oxide particles by AM.
- Cobalt oxide particle dissolution in acetate buffer was faster than in AM and decreased more rapidly with increasing pH.
Conclusions:
- Chloroquine alters phagolysosomal parameters but does not enhance cobalt oxide particle dissolution in rabbit AM.
- The phagolysosome environment influences particle dissolution differently than simple buffered solutions.
- A model was proposed to explain the observed differences in particle dissolution between AM and buffered saline.