Regulation of CXCL1 expression by IL-6 in cerebral endothelial cells
in vitro. a, Dark-field micrographs of brain sections collected from IL-6 knockout and wild-type mice killed 6 h after intraperitoneal injection of PTX (20 μg/kg) and analyzed for CXCL1 mRNA by in situ hybridization. Positively labeled cells (arrows) are seen only in the wild-type mouse (representative of 6 mice per genotype). Scale bar = 50 μm. b, Quantification of CXCL1 expression by quantitative RT-PCR or ELISA in cultures of bEnd.3 cerebral endothelial cells exposed for 3 h to IL-6 (10 ng/ml), soluble IL-6 receptor (IL-6Rα, 1 μg/ml), and/or neutralizing anti-IL-6 antibody (40 μg/ml). SOCS3 and ICAM1 mRNAs were used as a positive or negative control, respectively. The PCR data were compared with the Kruskal-Wallis test (P-values as indicated) followed by post hoc Wilcoxon tests. The ELISA data were compared using ANOVA (P-value as indicated) followed by post hoc Student's t tests. *Significantly different from the control group. n = 6 per condition.