The mosaic of autoimmunity: Hormonal and environmental factors involved in autoimmune diseases - 2008 Academic Article uri icon

abstract

  • Circadian rhythms are driven by biological clocks and are endogenous in origin [1]. Therefore, circadian changes in the metabolism or secretion of endogenous glucocorticoids are responsible, in part, for the time-dependent changes observed in the immune/inflammatory response and related clinical symptoms (e.g., arthritis). Recently, another circadian hormone, melatonin – the secre-tory product of the pineal gland – was found to be implicated in the time-dependent inflammatory reaction with effects opposite to those of cortisol, and as such, generates immune-potentiating activities. Interestingly, cortisol and melatonin show an opposite response to light [2]. The light conditions in the early morning have a strong impact on the morning cortisol peak, whereas melatonin is synthesized in a strictly nocturnal pattern. Reduced daily light exposure in northern Europe, at least during the winter, might explain the higher and more prolonged melatonin concentrations, as well as some epidemiological features concern-ing the prevalence of autoimmune diseases such as rheumatoid arthritis, that are observed in northern Europeans versus southern Europeans [3]. A diurnal rhythmicity in healthy humans between cellular (Th1 type) and humoral (Th2 type) immune responses was recently found and was related to the immunomodulatory actions of cortisol (decrease) and melatonin (increase) [4]. The interferon-gamma/interleukin-10 ratio peaks during the early morning and correlates negatively with plasma cortisol and positively with plasma melatonin. Accordingly, the intensity of arthritic pain varies consistently as a function of the hour of the day: pain is

publication date

  • January 1, 2008