Neuroendocrine-immune interactions in healthy aging

Abstract

Aim: The nervous, endocrine and immune systems are connected by shared neurotransmitters, hormones and cytokines. The function of these systems shows patterns of circadian rhythmicity and a number of age-related changes in the 24-h hormonal and non-hormonal rhythms have been found in older human beings. The aim of this study was to evaluate integration among the nervous, endocrine and immune systems in the elderly.Methods: Cortisol and melatonin serum levels were measured and lymphocyte subpopulation analyses were performed on blood samples collected every 4 h for 24 h from 15 healthy young-middle-aged subjects (range 36-55 years, mean age ± standard error [SE] 44.08 ± 1.76) and 15 healthy old-aged subjects (range 67-79 years, mean age ± SE 68.52 ± 1.27).Results: There was a statistically significant difference between the groups in the observed values of CD20 (total B cells higher in young-middle-aged subjects, P = 0.02), CD25 (activated T cells with expression of the α-chain of interleukin-2 receptor, higher in elderly subjects, P = 0.04) and DR+ T cells (activated T cells higher in elderly subjects, P = 0.01). There were different correlations among lymphocyte subpopulations and hormone serum levels in young and middle-aged subjects in compared to old-aged subjects. In the group of young-middle-aged subjects, a clear circadian rhythm was validated for the time-qualified changes of all the factors studied. In the group of elderly subjects, a clear circadian rhythm was validated for the nyctohemeral changes of CD3 (with a phase delay of 3 h), CD8, CD4/CD8 ratio, CD16, CD25 (in opposite phase), cortisol (with a phase delay of 1 h) and melatonin.Conclusion: The results of the current study show that aging is associated with enhanced responsiveness of the T-cell compartment, impairment of B-cell compartment and alterations in temporal architecture and correlations of neuroendocrine-immune parameters. © 2010 Japan Geriatrics Society.