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Effects of spermidine on function and ultrastructure of alveolar macrophages
A G Bulychev1, A Johansson, M Lundborg
1Institute of Cytology of the Academy of Sciences of Russia, St. Petersburg.
Abstract:
It is known that spermidine and other naturally occurring polyamines accumulate in rat lung slices by an energy-dependent uptake process and that alveolar macrophages (AM) have a greater rate of uptake than has the total lung cell population. In the present study rat AMs were incubated with spermidine, which resulted in a marked and significant (P < 0.002) decrease in phagocytosis of heat-killed yeast cells at concentrations 0.2 and 0.5 mM and a tendency to decrease at 0.05 mM. The number of microtubules surrounding the centrioles was measured using electron microscopy and appeared to be decreased at concentrations 0.2 and 0.5 mM. There was no affect on phagolysosomal pH. The results suggest that spermidine might affect the defense against inhaled pollutants and microbes, especially when spermidine levels are increased, as they are under conditions with high mitotic activity, e.g., in tumors.
Insights
Spermidine, a naturally occurring polyamine, impairs the phagocytic defense function of rat alveolar macrophages (AMs). This spermidine-induced reduction in macrophage activity may impact lung defense against inhaled pollutants and microbes.
Area of Science:
- Cell Biology
- Immunology
- Toxicology
Background:
- Naturally occurring polyamines, like spermidine, accumulate in rat lung slices via energy-dependent uptake.
- Alveolar macrophages (AMs) exhibit a higher uptake rate of polyamines compared to the total lung cell population.
Purpose of the Study:
- To investigate the effect of spermidine on the phagocytic activity of rat alveolar macrophages.
- To explore potential mechanisms underlying spermidine's impact on macrophage function.
Main Methods:
- Rat alveolar macrophages were incubated with varying concentrations of spermidine.
- Phagocytosis of heat-killed yeast cells was measured.
- Microtubule numbers surrounding centrioles were quantified using electron microscopy.
- Phagolysosomal pH was assessed.
Main Results:
- Spermidine significantly decreased yeast cell phagocytosis by AMs at concentrations of 0.2 and 0.5 mM, with a decreasing tendency at 0.05 mM.
- Electron microscopy revealed a reduction in the number of microtubules surrounding centrioles at higher spermidine concentrations.
- No significant effect of spermidine was observed on phagolysosomal pH.
Conclusions:
- Spermidine impairs the phagocytic capacity of alveolar macrophages, potentially compromising lung defense mechanisms.
- The observed reduction in microtubules suggests a possible mechanism for spermidine-induced functional impairment.
- Elevated spermidine levels, as seen in conditions of high mitotic activity, may negatively affect the lung's ability to combat inhaled pathogens and pollutants.