Influenza virus-induced glucocorticoid and hypothalamic and lung cytokine mRNA responses in dwarf lit/lit mice

Influenza virus infection up-regulates cytokines such as interleukin-1 beta (IL-1 beta) and activates the somatotropic axis and the hypothalamic-pituitary axis. Mice with deficits in growth hormone releasing hormone (GHRH) signaling (lit/lit mice) respond to influenza virus challenge with a progressive decrease in sleep and lower survival rates. Current experiments characterize plasma glucocorticoid responses and hypothalamic and lung mRNA expression of sleep-related genes in lit/lit mice and their heterozygous controls after influenza virus challenge. lit/lit mice had higher basal and post-infection plasma corticosterone levels compared to controls. In contrast, the heterozygous mice increased hypothalamic GHRH-receptor, CRH-type 2 receptor, IL-1 beta, and tumor necrosis factor-alpha (TNF-alpha) mRNAs after virus treatment while the lit/lit mice failed to up-regulate these substances. In contrast, lung levels of IL-1 beta and TNF-alpha mRNAs were greater in the lit/lit mice. These data are consistent with the hypothesis that the sleep response to influenza infection is mediated, in part, by an up-regulation of hypothalamic sleep-related transcripts and they also show that a primary deficit in GHRH signaling is associated with enhanced corticosterone secretion and attenuated hypothalamic cytokine response to infection. (c) 2006 Published by Elsevier Inc.