Inhibition of COX-2 reduces the age-dependent increase of hippocampal inflammatory markers, corticosterone secretion, and behavioral impairments in the rat

Brain aging as well as brain degenerative processes with accompanying cognitive impairments are generally associated with hyperactivity of the hypothalamus-pituitary-adrenal axis, the end product of which, the glucocorticoid hormone, has been warranted the role of cell damage primum movens ("cascade hypothesis"). However, chronic inflammatory activity occurs in the hippocampus of aged rats as well as in the brain of Alzheimer's disease patients. The concomitant increase in the secretion of the glucocorticoid hormone, the endogenous anti-inflammatory and pro-inflammatory markers, has prompted us to investigate the two phenomena in the aging rat, and to work out its meaning. This study shows that: (I) interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), and prostaglandin E-2 (PGE(2)) increase with age in the rats hippocampus, and (II) chronic oral treatment with celecoxib, a selective cycloxygenase-2 (COX-2) inhibitor, is able to contrast the age-dependent increase in hippocampal levels of pro-inflammatory markers and circulating anti-inflammatory corticosterone, provided that it is started at an early stage of aging. Under these conditions, age-related impairments in cognitive ability may be ameliorated. Taken together, these results indicate that there is a natural tendency to offset the age-dependent increase in brain inflammatory processes via the homeostatic increase of the circulating glucocorticoid hormone. (C) 2002 Wiley-Liss, Inc.