TY - JOUR T1 - The Type 1 Interleukin-1 Receptor Is Essential for the Efficient Activation of Microglia and the Induction of Multiple Proinflammatory Mediators in Response to Brain Injury JF - The Journal of Neuroscience JO - J. Neurosci. SP - 6071 LP - 6082 DO - 10.1523/JNEUROSCI.22-14-06071.2002 VL - 22 IS - 14 AU - Anirban Basu AU - J. Kyle Krady AU - Mark O'Malley AU - Scott D. Styren AU - Steven T. DeKosky AU - Steven W. Levison Y1 - 2002/07/15 UR - http://www.jneurosci.org/content/22/14/6071.abstract N2 - Interleukin-1 (IL-1) is induced immediately after insults to the brain, and elevated levels of IL-1 have been strongly implicated in the neurodegeneration that accompanies stroke, Alzheimer's disease, and multiple sclerosis. In animal models, antagonizing IL-1 has been shown to reduce cell death; however, the basis for this protection has not been elucidated. Here we analyzed the response to penetrating brain injury in mice lacking the type 1 IL-1 receptor (IL-1R1) to determine which cellular and molecular mediators of tissue damage require IL-1 signaling. At the cellular level, fewer amoeboid microglia/macrophages appeared adjacent to the injured brain tissue in IL-1R1 null mice, and those microglia present at early postinjury intervals retained their resting morphology. Astrogliosis also was mildly abrogated. At the molecular level, cyclooxygenase-2 (Cox-2) and IL-6 expression were depressed and delayed. Interestingly, basal levels of Cox-2, IL-1, and IL-6 were significantly lower in the IL-1R1 null mice. In addition, stimulation of vascular cell adhesion molecule-1 mRNA was depressed in the IL-1R1 null mice, and correspondingly, there was reduced diapedesis of peripheral macrophages in the IL-1R1 null brain after injury. This observation correlated with a reduced number of Cox-2+ amoeboid phagocytes adjacent to the injury. In contrast, several molecular aspects of the injury response were normal, including expression of tumor necrosis factor-α and the production of nerve growth factor. Because antagonizing IL-1 protects neural cells in experimental models of stroke and multiple sclerosis, our data suggest that cell preservation is achieved by abrogating microglial/macrophage activation and the subsequent self-propagating cycle of inflammation. ER -