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Macrophage phagocytosis and membrane fluidity in mice: the effect of age and dietary protein
Abstract:
Male C57BL/6NNia mice were used to investigate the effects of age and dietary protein intake on Fc and C3b receptor-mediated phagocytosis and on membrane fluidity. Six-month-old (adult) and 24-month-old (aged) mice were fed a 6% or 25% protein diet for 3, 5, or 6 weeks at which time thioglycollate elicited peritoneal macrophages were isolated. Both binding of IgG-coated sheep red blood cells to the macrophages and ingestion via the Fc-receptor were identical in all 4 groups after 3 and 6 weeks of feeding but were decreased at 5 weeks in the aged animals fed 6% protein. Phagocytosis via the C3b receptor was not depressed in either age group fed the low protein diet; it was, however, augmented significantly in the aged animals fed the 25% protein diet for 5 and 6 weeks. Membrane fluidity of the plasma membrane outer hemileaflet was monitored with an impermeant fluorescent probe. No changes were observed between adult and aged mice maintained up to 6 weeks on the diets.
Insights
Dietary protein impacts immune cell function in aging mice. Aged mice on low protein diets showed reduced Fc receptor phagocytosis, while high protein diets enhanced C3b receptor activity.
Area of Science:
- Immunology
- Gerontology
- Nutrition Science
Background:
- Aging affects immune system function, including macrophage phagocytosis.
- Dietary protein intake is crucial for maintaining immune cell activity.
- Understanding these interactions is key to promoting health in older adults.
Purpose of the Study:
- To investigate how age and dietary protein levels influence Fc and C3b receptor-mediated phagocytosis in mice.
- To assess the impact of these factors on macrophage membrane fluidity.
- To identify potential nutritional strategies to support immune function in aging.
Main Methods:
- Male C57BL/6NNia mice (adult and aged) were fed 6% or 25% protein diets for 3-6 weeks.
- Thioglycollate-elicited peritoneal macrophages were isolated for functional assays.
- Fc and C3b receptor-mediated phagocytosis of IgG-coated sheep red blood cells was measured.
- Plasma membrane fluidity was assessed using a fluorescent probe.
Main Results:
- Fc receptor-mediated phagocytosis decreased at 5 weeks in aged mice on a 6% protein diet.
- C3b receptor-mediated phagocytosis was not affected by low protein but was enhanced in aged mice on a 25% protein diet (5-6 weeks).
- No significant changes in plasma membrane fluidity were observed between age groups or diet conditions.
Conclusions:
- Dietary protein intake modulates Fc and C3b receptor-mediated phagocytosis differently in aged mice.
- High protein diets may enhance certain immune functions in aging.
- Macrophage membrane fluidity appears unaffected by short-term dietary protein variations in this model.