[Neuroendocrine immune interactions in rheumatic diseases]

Clinical observations in chronic inflammatory diseases have demonstrated the significant influence of neuroendocrine mechanisms on the immune system: (1) Amelioration of rheumatoid arthritis during pregnancy; (2) preponderance of women versus men with respect to autoimmune diseases; (3) negative effects of ovulation-inducing therapy, oral contraceptives, and hormone replacement therapy; (4) protective effect of hemiplegia; (5) influence of psychological stress on inflammation; and (6) influence of circadian rhythms on inflammatory symptoms.The effects of different hormones and neurotransmitters on the immune system are influenced by: (1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses, (2) the cell types involved during different phases of the disease, (3) the target organ with its specific microenvironment, (4) the timing of hormone or neurotransmitter increase in relation to the disease course, (5) the concentration of hormones and neurotransmitters, (6) the variability in expression of receptors depending on the microenvironment and the cell type, and (7) the intra- and extracellular peripheral metabolism of hormones and neurotransmitters leading to important biologically active metabolites with quite different anti- and proinflammatory functions.The circadian rhythm of disease-related symptoms with a peak in the early morning hours confirms that the neuroendocrine system has a strong influence on these chronic immune/inflammatory diseases. The influence is transmitted by the circadian fluctuation in the activity of hormonal and neuronal pathways linking the brain to immune cell activation.These considerations could lead to novel therapeutic strategies for rheumatic diseases in the future.