Infection negatively impacts mental health. Sick individuals become lethargic, experience cognitive deficits and malaise, and lose interest in social contact and other usual daily activities. Prominent among the changes in CNS processes during infection are alterations in sleep. Cytokines, such as interleukin (IL)-1, tumor necrosis factor (TNF), and IL-6 are upregulated during infection. Two lines of evidence suggest that infection-induced alterations in sleep are mediated by actions of these cytokines in brain. First, numerous studies indicate IL-1, TNF, and IL-6 regulate/modulate physiological sleep in the absence of immune challenge. Second, experimental models for which alterations in sleep have been determined are associated with increases in these same cytokines. The involvement of IL-1, TNF, and IL-6 in the regulation of sleep, and the alterations in sleep that occur during infections in which these cytokines are upregulated, have led to suggestions that infection-induced alterations of sleep are mediated by cytokines in brain. Although plausible, and based on empirical evidence, studies to directly test this hypothesis have not been conducted. The fundamental goal of this project is to determine how acute infections alter sleep. To achieve this goal we will use a clinically relevant murine model of infection, sepsis induced by cecal ligation and puncture. We propose experiments that focus on cytokines (IL-1, TNF, IL-6) as mediators of infection-induced alterations in sleep. We will: 1) determine the extent infection alters sleep and the impact of prior sleep loss on responses to infection; 2) quantify alterations in cytokine mRNA and protein in brain during infection; and 3) answer the question "Does interfering with cytokine actions in brain impact infection-induced alterations in sleep?" IL-1, TNF, and IL-6 have been the subject of intense investigation with respect to their peripheral roles in sepsis, and are known central regulators/modulators of sleep. As such, there is a strong conceptual framework within which to investigate the mechanistic relationships between sleep and sepsis, and mediators implicated in both processes. We present preliminary data that demonstrate long-term alterations in CNS function following acute peripheral infection. We demonstrate our ability to determine multiple facets of sleep-wake behavior of mice and to target cytokine systems in brain. Successful completion of the proposed studies will provide information critical to understanding how infection impacts CNS function, as evidenced by alterations in sleep.

R01HL080972

2004-09-27

2009-05-31