[Note: See article discussing these findings and speculating “It is also possible that TNF-a is the explanation for the scourge called Chronic Fatigue Syndrome,” at Economist.com, July 19, 2007 ]
Production of TNF-a and IL-1 in infectious and autoimmune diseases is associated with fever, fatigue, and sleep disturbances, which are collectively referred to as sickness behavior syndrome. In mice TNF-a and IL-1 increase nonrapid eye movement sleep.
Because clock genes regulate the circadian rhythm and thereby locomotor activity and may alter sleep architecture we assessed the influence of TNF-a on the circadian timing system. TNF-a is shown here to suppress the expression of the PAR bZip clock-controlled genes Dbp, Tef, and Hlf and of the period genes Per1, Per2, and Per3 in fibroblasts in vitro and in vivo in the liver of mice infused with the cytokine.
The effect of TNF-a on clock genes is shared by IL-1b, but not by IFN-a , and IL-6. Furthermore, TNF-a interferes with the expression of Dbp in the suprachiasmatic nucleus and causes prolonged rest periods in the dark when mice show spontaneous locomotor activity. Using clock reporter genes TNF-a is found here to inhibit CLOCK-BMAL1-induced activation of E-box regulatory elements-dependent clock gene promoters.
We suggest that the increase of TNF-a and IL-1b, as seen in infectious and autoimmune diseases, impairs clock gene functions and causes fatigue.
Source: Proceedings of the National Academy of Sciences. July 31, 2007, vol. 104, no. 31, pp. 12843-12848, 10.1073/pnas.0701466104, by Cavadini G, Petrzilka S, Kohler P, Jud Corinne, Tobler I, Birchler T, Fontana A. Division of Clinical Immunology, University Hospital Zurich, Zurich, Switzerland; Institute of Biochemistry, University of Fribourg, Fribourg, Switzerland; Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland. [E-mail: Thomas.email@example.com or Adriano.firstname.lastname@example.org ]