Matrix metalloproteinases (MMPs) belong to a class of extracellular proteinases responsible for maintaining and remodeling the extracellular matrix. In addition to multiple functions in normal physiology, abnormal MMP expression and activity may also participate in the pathophysiology of cerebral disease. Here, we show that MMP-9 (gelatinase B; EC.3.4.24.35) contributes to the pathophysiology of traumatic brain injury. After controlled cortical impact in mice, MMP-9 was increased in traumatized brain. Total MMP-9 levels at 24 hr were significantly increased as measured by a substrate cleavage assay. Zymograms showed that MMP-9 was elevated as early as 3 hr after traumatic brain injury, reaching a maximum at approximately 24 hr. Increased MMP-9 levels persisted for up to 1 week. Western blot analysis indicated increased profiles of MMP-9 expression that corresponded with the zymographic data. Knock-out mice deficient in MMP-9 gene expression were compared with wild-type littermates in terms of morphological and motor outcomes after trauma. Motor outcomes were measured at 1, 2, and 7 d after traumatic brain injury by the use of a rotarod device. MMP-9 knock-out mice had less motor deficits than wild-type mice. At 7 d, traumatic brain lesion volumes on Nissl-stained histological sections were significantly smaller in MMP-9 knock-out mice. These data demonstrate that MMP-9 contributes to the pathophysiology of traumatic brain injury and suggest that interruption of the MMP proteolytic cascade may be a possible therapeutic approach for preventing the secondary progression of damage after brain trauma.

Long-term memory formation is regulated by many distinct molecular mechanisms that control gene expression. An emerging model for effecting a stable, coordinated pattern of gene transcription involves epigenetic tagging through modifications of histones or DNA. In this study, we investigated the regulation of histone phosphorylation in the hippocampus by the ERK/MAPK (extracellular signal-regulated kinase/mitogen-activated protein kinase) pathway. We found that activation of ERK/MAPK in vitro significantly increased histone H3 phosphorylation in hippocampal area CA1. Furthermore, we found that contextual fear conditioning in vivo leads to a rapid time-dependent increase in histone H3 phosphorylation in area CA1. This increase paralleled the time course of contextual fear-dependent activation of ERK, and was inhibited in vivo by a latent inhibition paradigm as well as by injection of an N-methyl-D-aspartic acid receptor (NMDA-R) antagonist. Finally, injection of an inhibitor of MEK (MAP kinase/ERK kinase), the unique dual-specificity kinase upstream of ERK, blocked the increase in histone H3 phosphorylation seen after contextual fear conditioning. These results demonstrate that changes in histone phosphorylation in the hippocampus are regulated by ERK/MAPK following a behavioral fear conditioning paradigm.Long-term memory formation is a complex process involving biochemical signaling cascades that lead to a change in gene expression in neurons. In mammalian associative memory tasks, activation of the ERK/MAPK (extracellular signal-regulated kinase/mitogen-activated protein kinase) cascade in the hippocampus is necessary for consolidation of the memory (Atkins et al. 1998). This is accomplished typically by activation of the NMDA (N-methyl-D-aspartic acid) subtype of glutamate receptors, leading to an increase in intracellular Ca 2+ (Fanselow et al. 1994). Ca 2+ activates Ca 2+-sensitive protein kinase C (PKC) and adenylyl cyclase/protein kinase A (PKA), triggering a series of events that eventually converge upon ERK (Adams and Sweatt 2002). Once activated, ERK translocates into the nucleus to coordinate and effect changes in gene expression (Davis et al. 2000). ERK is known to regulate transcription factors such as CREB (Crebinding protein) and Elk-1 (Sweatt 2001), which help initiate transcription of memory-associated genes that contain their respective regulatory elements.There is growing evidence that memory formation also utilizes epigenetic mechanisms that modify the structure of chromatin (Swank and Sweatt 2001;Guan et al. 2002;Alarcon et al. 2004;Korzus et al. 2004;Wood et al. 2005; for review, see Levenson and Sweatt 2005). Epigenetic modifications can serve as enduring changes to the epigenome that help drive stable changes in gene expression (Rakyan et al. 2001), which in turn manifest as a long-lasting change in behavior. Mechanistically, this is accomplished by direct modification of DNA or posttranslational modification of histone proteins, including methylation, acetylation, and phosphorylation (Ber...

The extracellular signal-regulated kinase (ERK)/MAPK (mitogen-activated protein kinase) cascade has been established as a potent regulator of gene transcription in long-term memory formation, but the precise mechanisms of this regulation are poorly understood. ERK does not directly affect many of its nuclear targets, but rather must act through intermediary kinases. In this study, we investigated the role of mitogen-and stress-activated protein kinase 1 (MSK1), a nuclear kinase downstream of ERK, in chromatin remodeling during hippocampus-dependent memory formation. Mice lacking MSK1 show impaired Pavlovian fear conditioning and spatial learning, as well as a deficiency in histone phosphorylation and acetylation in the hippocampus after fear training. In addition, hippocampal slices from MSK1 knock-out mice exhibit a deficiency in both histone phosphorylation and acetylation after activation of the ERK pathway in vitro. In vivo injections of a histone deacetylase inhibitor, sodium butyrate, fail to alleviate the fear conditioning deficit in MSK1 knock-out mice. Finally, MSK1 knock-out mice demonstrate a deficiency in cAMP response element-binding protein (CREB) phosphorylation after fear training, which persists after sodium butyrate injection. This suggests that CREB phosphorylation and histone acetylation represent parallel targets of MSK1 function. Our study identifies MSK1 as an important regulator of chromatin remodeling in long-term memory.

The aim of the study was to determine the antiangiogenic efficacy of vatalanib, sunitinib, and AMD3100 in an animal model of human glioblastoma (GBM) by using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and tumor protein expression analysis. Orthotopic GBM-bearing animals were randomly assigned either to control group or vatalanib, sunitinib, and AMD3100 treatment groups. Following 2 weeks of drug treatment, tumor growth and vascular parameters were measured using DCE-MRI. Expression of different angiogenic factors in tumor extracts was measured using a membrane-based human antibody array kit. Tumor angiogenesis and invasion were determined by immunohistochemistry. DCE-MRI showed a significant increase in tumor size after vatalanib treatment. AMD3100-treated group showed a significant decrease in a number of vascular parameters determined by DCE-MRI. AMD3100 significantly decreased the expression of different angiogenic factors compared to sunitinib or vatalanib; however, there were no significant changes in vascular density among the groups. Sunitinib-treated animals showed significantly higher migration of the invasive cells, whereas in both vatalanib- and AMD3100-treated animals the invasive cell migration distance was significantly lower compared to that of control. Vatalanib and sunitinib resulted in suboptimal therapeutic effect, but AMD3100 treatment resulted in a significant reduction in tumor growth, permeability, interstitial space volume, and invasion of tumor cells in an animal model of GBM.