P. Mancuso et al., Evaluation of phagocytosis and arachidonate metabolism by alveolar macrophages and recruited neutrophils from F344xBN rats of different ages, MECH AGE D, 122(15), 2001, pp. 1899-1913
The incidence of infectious respiratory diseases increases with aging. Resi
dent alveolar macrophages (AMs) and recruited leukocytes (PMNL) mediate cel
lular defense against bacterial infections in the lung, and phagocytosis an
d lipid mediator synthesis are important components of their antimicrobial
capacity. The objective of this study was to determine if either phagocytic
capacity or lipid mediator generation declines with normal aging, in eithe
r AMs or PMNL recruited to a site of inflammation. The F344xBN rat hybrid h
as a lower incidence of pathologies associated with aging, particularly up
to 20 months; animals aged 6, 12 and 18 months were chosen to evaluate chan
ges associated with normal aging. As previously reported for peripheral blo
od leukocytes, phagocytosis by recruited PMNL declined with aging: recruite
d PMNL from 18 months rats showed a significantly decreased capacity to pha
gocytose live Klebsiella pneumoniae bacteria, compared to PMNL from 6 month
s rats. Surprisingly, however, the phagocytic capacity of AMs increased wit
h aging: the phagocytic index of AMs from 18 months rats was more than thre
e times that of AMs from 6 months rats. The capacity of AMs and recruited P
MNL to release arachidonic acid or synthesize leukotrienes or prostaglandin
s did not change with aging. This study demonstrates that, although phagocy
tosis by recruited PMNL declines with aging, other aspects of immune functi
on do not decline, and may actually increase, with normal aging. These resu
lts suggest that impaired phagocytosis by recruited PMNL may be an importan
t component of the increased susceptibility to infectious respiratory disea
ses during normal aging. (C) 2001 Published by Elsevier Science Ireland Ltd
.