S100B protein (S100B) has been described as a marker of brain injury. Various cytokines also increase in the cerebrospinal fluid (CSF) of patients with severe traumatic brain injury (TBI). Thus, we investigated early changes in the concentrations of CSF S100B and various cytokines after TBI and evaluated the relations of both S100B and cytokines to intracranial pressure (ICP) and prognosis. Twenty-three patients with severe TBI and a Glasgow Coma Scale score of 8 or less on admission were included in this study. CSF and serum samples were obtained on admission and at 6, 12, 24, 48, 72, and 96 h after injury. CSF concentrations of S100B and CSF and serum concentrations of five cytokines (IL-1beta, TNF-alpha, IL-6, IL-8, and IL-10) were measured and compared. The CSF S100B concentration was increased for 6 h after injury and decreased thereafter. The CSF concentrations of IL-6 and IL-8 peaked within 6 h after injury; other cytokines (IL-1beta, TNF-alpha, and IL-10) were elevated for 24 h after injury and gradually decreased thereafter. Peak CSF S100B concentrations correlated significantly with ICP determined at the time CSF samples were taken (r = 0.729, P < 0.0001). For the cytokines investigated, only the peak CSF IL-1beta concentration correlated significantly and positively with the peak CSF S100B concentration (r = 0.397, P < 0.005). Peak CSF concentrations of S100B (1649 +/- 415 microg/L, mean +/- SEM) and IL-1beta (16.5 +/- 3.3 pg/mL) in the 6 patients with high ICP were significantly higher than those (233 +/- 67 microg/L, 7.6 +/- 1.7 pg/mL, respectively) in the 17 patients with low ICP (P < 0.05). The CSF S100B concentration (1231 +/- 378 microg/L) in eight patients with an unfavorable outcome was significantly higher than that (267 +/- 108 microg/L) in 15 patients with a favorable outcome (P < 0.05). The CSF IL-1beta concentration (14.8 +/- 3.4 pg/mL) in eight patients with an unfavorable outcome tended to be higher than that (7.3 +/- 1.5 pg/mL) in 15 patients with a favorable outcome (P = 0.057). CSF concentrations of S100B and cytokines peak within 24 h after severe TBI and decrease gradually thereafter. CSF S100B and IL-1beta may be useful as predictors of outcome in cases of severe TBI.

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Ischemic preconditioning (IPC), a procedure consisting of transient ischemia and subsequent reperfusion, provides ischemic tolerance against prolonged ischemia in the brain. Although the blood flow changes mediated by IPC are primarily perceived by vascular endothelial cells, the role of these cells in ischemic tolerance has not been fully clarified. In this study, we found that the P2X4 receptor, which is abundantly expressed in vascular endothelial cells, is required for ischemic tolerance following middle artery occlusion (MCAO) in mice. Mechanistically, the P2X4 receptor was stimulated by fluid shear stress, which mimics reperfusion, thus promoting the increased expression of osteopontin, a neuroprotective molecule. Furthermore, we found that the intracerebroventricular administration of osteopontin was sufficient to exert a neuroprotective effect mediated by preconditioning-stimulated P2X4 receptor activation. These results demonstrate a novel mechanism whereby vascular endothelial cells are involved in ischemic tolerance.

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