Chapter 3- Pro-inflammatory cytokines in learning and memory

AMAICHA MARA DEPINO

Learning and Memory Developments and Intellectual Disabilities

Nova Science Publishers, Inc.

Año: 2011; p. 73 - 103

In animals and in humans, cytokines are typically immune system molecules that help orchestrate the host responses to infection. Pro-inflammatory cytokines coordinate immune, physiological, metabolic and behavioral responses that are collectively termed the acute phase reaction. In addition to their role in immunoregulation of inflammatory processes, pro-inflammatory cytokines represent the major communication link between peripheral immunity and the central nervous system. Cytokines are known to play a role in the physiological and behavioral adjustments that occur during sickness, leading to ―sickness behavior‖. One of the most salient symptoms of the sickness behavior syndrome is alteration in learning and memory processes. Studies in animals have demonstrated that acute activation of pro-inflammatory cytokine signaling in the brain in response to peripheral immune activation is associated with deficits in hippocampal-dependent memory. Recent studies suggest that brain cytokines may also have some physiological roles in neural, neuroendocrine, and behavioral regulation in non-pathological situations. Cytokine-induced modulation of memory processes is a complex phenomenon, including both detrimental and beneficial effects, depending on the specific pro-inflammatory cytokine, its levels (particularly within the brain), and the particular condition that elicits the cytokine secretion. Some cytokines, e.g., Interleukin (IL)-1, have been shown to significantly influence memory consolidation. IL-1, IL-6 and tumor necrosis factor (TNF)-a are the main cytokines involved in learning and memory modulation. These behavioral data are consistent with the impairing effect of enhanced cytokine signaling on hippocampal long-term potentiation. We will review the literature, including our own contribution, on human and animal model studies of the role of cytokines in learning and memory.