Chemokines/intercrines are structurally and functionally related cytokines that induce specific actions on the immune system and are released in response to infection, inflammation, and trauma. These pathological processes are frequently accompanied with food intake suppression. In the present study, the action of chemokines/intercrines on the regulation of feeding was investigated using the intracerebroventricular microinfusion of chemokine/intercrine-alpha subfamily members [interleukin-8 (IL-8); growth-related cytokine/melanoma growth-stimulating activity (GRO-alpha/MGSA); platelet factor-4 (PF-4); beta-thromboglobulin (beta-TG); and interferon-inducible protein-10 (IP-10)] and beta-subfamily members [monocyte chemotactic protein-1/monocyte chemotactic and activating factor (MCP-1/MCAF); regulated upon activation normal T-cell expressed and presumably secreted (RANTES); macrophage inflammatory protein-1 alpha (MIP-1 alpha); and macrophage inflammatory protein-1 beta (MIP-1 beta)]. The doses administered were 1.0, 20, and 100 ng/rat of the chemokine/intercrine. The intracerebroventricular administration of three members of the alpha-subfamily (IL-8, PF-4, and IP-10) and two members of the beta-subfamily (MCP-1/MCAF and RANTES) decreased the short-term (2-h) food intake. These effective chemokines/intercrines, however, were significantly less potent than IL-1 beta in decreasing feeding. The results support the hypothesis that only a subset of immunomodulators released during pathological processes may participate in the regulation of feeding with different potencies.
Interleukin-8 (IL-8) is released in response to infection, inflammation, and trauma. The most important stimuli for IL-8 release during these pathological processes are IL-1, tumor necrosis factor, and bacterial lipopolysaccharide (endotoxin), factors that have been shown to suppress feeding. In the present study, the participation of IL-8 on the central regulation of feeding was investigated. Intracerebroventricular (icv) microinfusion of recombinant human IL-8 (rhIL-8, 1.0-100 ng/rat) suppressed the short-term (2-h) food intake. The most effective dose of rhIL-8, 20 ng, decreased 2-h food intake by 25% and nighttime food intake by 23%. Intracerebroventricular microinfusion of anti-rhIL-8 antibody (200 and 500 ng) blocked the effect of 20 ng rhIL-8 on 2-h and nighttime food intakes. Computerized analysis of behavioral patterns for the 2-h period demonstrated a specific reduction of meal size (by 33%), whereas meal frequency and meal duration were not affected after the icv microinfusion of 20 ng rhIL-8. This short-term food intake suppression by icv rhIL-8 was accompanied by a small, but significant, increase in cerebrospinal fluid-brain and rectal temperatures. Intraperitoneal administration of rhIL-8 in doses equivalent to those administered centrally had no effect on food intake. The results suggest that IL-8 acts directly in the central nervous system to decrease feeding. This effect of IL-8 may contribute to the food intake suppression frequently accompanying pathological processes.
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