Interrelationship among neutrophil efficiency, inflammation, antioxidant activity and zinc pool in very old age

Neutrophils are the first barrier against infections. Aged neutrophils display impaired oxidative burst and phagocytosis with subsequent less capability to destroy bacteria. In successful ageing (nonagenarians), neutrophil efficiency (phagocytosis) increases. After ingested microbes, aged neutrophils are less prone to undergo apoptosis favouring chronic inflammation. Moreover, the superoxide dismutase (SOD) activity, which is necessary in avoiding ROS produced by oxidative burst, is limited in ageing. The mechanisms of age-related changes in neutrophil function are not fully understood, taking also into account that nonagenarians escape infections in comparison with elderly. Zinc pool may be involved because it is pivotal for neutrophil efficiency and SOD activity. Since zinc also controls the inflammation, via IL-6 and soluble factor of gp130 (sgp130), we have assessed the possible interrelationship among oxidative burst, apoptosis, inflammation, SOD, adhesion molecule Mac-1 and zinc pool in elderly and in nonagenarians. The oxidative burst and the capacity to increase Mac-1 after PMA stimulation decrease both in elderly and nonagenarians, but the latter display a slight increased neutrophil induced apoptosis, decreased sgp130, increased SOD, and more neutrophil zinc content, as it occurs in young-adults. Significant correlation exists between sgp130 and zinc pool in very old age. These findings suggest lower chronic inflammation in nonagenarians, via more zinc available, with subsequent long-life survival. Therefore, a more correct interrelationship among neutrophil efficiency, inflammation, antioxidant activity and zinc pool exists in successful ageing with subsequent more effectiveness to control the inflammatory response to pathogens.