The macrophage in cell biology of aging.
Peritoneal macrophages (PM) offer a convenient system to study biochemical and physiological aspects of cellular aging, as well as gene expression, signal transduction and cytoplasmic functions. They are harvested directly from animals whose ages are well defined, and in good yields. PM are easily maintained in culture, and their unique physiological or biochemical characteristics can be manipulated either in-vivo or in-vitro. During inflammation, or upon interaction with soluble or particulate stimuli and consequent phagocytosis, macrophages undergo respiratory burst activation, producing large quantities of superoxide anions by NADPH oxidase. Increased superoxide production in response to zymosan was found in resident PM from senescent mice. These were non-specifically activated as compared to young, as shown also by increased tissue transglutaminase (TGase) activity, and increased cell yield. Moreover, PM from senescent mice were not affected by the retinoid induced up-regulation of TGase activity or down-regulation of superoxide release, as were PM from young mice. Also, altered receptor function and enzymic activities were demonstrated. Thus, apart from its function in immunity, the macrophage offers the possibility to study cell biology of aging as well.
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