Association between circadian rhythms of endogenous hypothalamic opioid peptides and of natural killer cell activity.
To explore in man the hypothesis that natural killer cell activity and hypothalamic-hypophyseal hormones constitute a mutually coupled multioscillatory system, we analysed and compared, in 11 healthy volunteers, the circadian variations in plasma concentrations of beta-endorphin, met-enkephalin and alpha-MSH, and of natural killer activity of peripheral blood lymphocytes. Natural killer cell activity and plasma beta-endorphin levels showed a similar circadian rhythm with the peak in the morning (acrophases at 06.14 and 08.25, respectively), whereas the circadian rhythm of met-enkephalin was approximately in antiphase to the natural killer rhythm (acrophase close to 17,00 hours). Although daily variation of alpha-MSH showed greater inter-individual variability, a circadian rhythm was statistically validated. Analysis of correlation between rhythmometric parameters (mesor, amplitude, peak and nadir) of natural killer cell activity vs neuro-endocrine hormones revealed that the minimum and medium daily concentrations of beta-endorphin correlated directly with the corresponding parameters of natural killer activity, while the maximum and medium concentrations of met-enkephalin were inversely correlated with the peak and the mesor of natural killer activity. The amplitude of natural killer cell activity oscillations correlated directly with the peak, mesor and nadir concentrations of alpha-MSH. We show here that circadian rhythms of some neuroendocrine hormones of the hypothalamic-hypophyseal axis, i.e. beta-endorphin, met-enkephalin and alpha-MSH, are significantly coupled to daily oscillations of NK cell activity.
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2nd Department of Dermatology, University of Milano, Italy.
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D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D004744:Enkephalin, Methionine / Q000097:blood; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007694:Killer Cells, Natural / Q000502:physiology*; D008875:Middle Aged; D015213:Neuroimmunomodulation / Q000502:physiology*; D000521:alpha-MSH / Q000097:blood; D001615:beta-Endorphin / Q000097:blood
D000521:alpha-MSH; D004744:Enkephalin, Methionine; D001615:beta-Endorphin