Decreased brain damage and curtailed inflammation in transcription factor CCAAT/enhancer binding protein b knockout mice following transient focal cerebral ischemia Ramya Kapadia,* ,  Kudret Tureyen,* Kellie K. Bowen,* Haviryaji Kalluri,* Peter F. Johnson,§ and Raghu Vemuganti* ,   , à *Department of Neurological Surgery,  Neuroscience Training Program and àCardiovascular Research Center, University of Wisconsin, Madison, Wisconsin, USA §Laboratory of Protein Dynamics and Signaling, National Cancer Institute-Frederick, Frederick, Maryland, USA Abstract CCAAT/enhancer binding protein b (C/EBPb) is a leucine- zipper transcription factor that regulates cell growth and differentiation in mammals. Expression of many pro-inflam- matory genes including the cytokine interleukin-6 is known to be controlled by C/EBPb. We report that focal cerebral isc- hemia induced by transient middle cerebral artery occlusion (MCAO) significantly increases C/EBPb gene expression in mouse brain at between 6 and 72 h of reperfusion. To understand the functional significance of C/EBPb in postis- chemic inflammation and brain damage, we induced transient MCAO in cohorts of adult C/EBPb null mice and their wild-type littermates. At 3 days of reperfusion following transient MCAO, C/EBPb null mice showed significantly smaller infa- rcts, reduced neurological deficits, decreased terminal de- oxynucleotidyl transferase-mediated dUTP nick-end labeling- positive cells, decreased intercellular adhesion molecule 1 (ICAM1) immunopositive vessels, decreased extravasated neutrophils and fewer activated microglia/macrophages, compared with their wild-type littermates. Furthermore, GeneChip analysis showed that postischemic induction of many transcripts known to promote inflammation and neur- onal damage was less pronounced in the brains of C/EBPb–/– mice compared with C/EBPb+/+ mice. These results suggest a significant role for C/EBPb in postischemic inflammation and brain damage. Keywords: gene expression, infarction, interleukin-6, micro- array, silencer factor-B, stroke. J. Neurochem. (2006) 98, 1718–1731. Acute inflammation is known to significantly contribute to secondary ischemic neuronal damage (Iadecola and Alexander 2001; Zheng et al. 2003). In experimental animals, increased expression of pro-inflammatory genes starts within hours and persists for days after focal ischemia (Stanimirovic and Satoh 2000; Schroeter et al. 2003). Several transcription factors including CCAAT/enhancer binding protein b (C/EBPb), Egr1, HIF1, IRF1, nuclear factor (NF)-jB, STAT3, c-fos, Received March 2, 2006; revised manuscript received April 11, 2006; accepted April 11, 2006. Address correspondence and reprint requests to Raghu Vemuganti, PhD, Department of Neurological Surgery, University of Wisconsin, K4/ 8 (Mail stop code CSC-8660), 600 Highland Avenue, Madison, WI 53792, USA. E-mail: vemugant@neurosurg.wisc.edu Abbreviations used: ATF, activating transcription factor; C/EBPb , CCAAT/enhancer binding protein b; CHOP, C/EBP homologous protein; CREB, cyclic AMP response element-binding protein; CREM, cyclic AMP responsive element modulator; EST, expressed sequence tag; G-CSF, granulocyte colony-stimulating factor; GFAP, glial fibrillary acidic protein; GSI-B4, Griffonia simplicifolia-IB4; H&E, hematoxylin and eosin; HIF, hypoxia inducible factor; HO, heme oxygenase; HSP, heat-shock protein; ICAM, intercellular adnesion molecule; IEG, immediate early gene; IFN, interferon; IGF, insulin- like growth factor; IL, interleukin; iNOS, inducible nitric oxide synthase; IRF, interferon regulatory factor; KO, knockout; MABP, mean arterial blood pressure; MCAO, middle cerebral artery occlusion; MCP, macrophage chemoattractant protein; M-CSF, macrophage colony stimulating factor; MLS, myeloid leukemia sequence; MMP, matrix metalloproteinase; Ms4a11, membrane spanning 4 domains, subfamily A, member 11; NF, nuclear factor; ODC, ornithine decarboxylase; PaCO 2 , arterial partial pressure of carbon dioxide; PaO 2 , arterial partial pressure of oxygen; PARP, poly ADP ribose polymerase; PBS, phosphate-buffered saline; rCBF, regional cerebral blood flow; SF, silencer factor; Sh, sham; STAT, signal transducer and activator of transcription; TNF, tumor necrosis factor; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; WT, wild type. Journal of Neurochemistry , 2006, 98, 1718–1731 doi:10.1111/j.1471-4159.2006.04056.x 1718 Journal Compilation Ó 2006 International Society for Neurochemistry, J. Neurochem. (2006) 98, 1718–1731 Ó 2006 The Authors