Tissue inhibitor of metalloproteinases-1 (TIMP-1) is differentially induced in neurons and astrocytes after seizures: evidence for developmental, immediate early gene, and lesion response

Regulation and function of tissue inhibitor of metalloproteinase (TIMP) 1 and TIMP3 in periovulatory rat granulosa cells

In the ovary, the matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinase (TIMPs) have been postulated to regulate extracellular matrix remodeling associated with ovulation. In the present study, we investigated the regulatory mechanisms controlling expression of Timp1 and Timp3 mRNA in periovulatory granulosa cells. Granulosa cells were isolated from immature pregnant mare serum gonadotropin-primed (10 IU) rat ovaries and treated with human chorionic gonadotropin (hCG; 1 IU/ml). At 4 h after hCG treatment, Timp1 expression was highest and then decreased gradually over the remaining 24 h of culture. In contrast, hCG induced a biphasic increase of Timp3 expression at 2 and 16 h. The hCG stimulated expression of Timp1 and Timp3 mRNA was blocked by inhibitors of the protein kinase A (H89), protein kinase C (GF109203), and MAPK (SB2035850) pathways. To further explore Timp1 and Timp3 regulation, cells were cultured with the progesterone receptor antagonist RU486, which blocked the hCG induction of Timp3 expression, whereas the epidermal growth factor receptor tyrosine kinase inhibitor AG1478 blocked the hCG stimulation of both Timp1 and Timp3 expression. The prostaglandin-endoperoxide synthase 2 inhibitor NS-398 had no effect. The potential function of TIMP3 was investigated with Timp3-specific small interfering RNA treatment. Timp3 small interfering RNA resulted in a 20% decrease in hCG-induced progesterone levels and microarray analysis revealed an increase in cytochrome P450 Cyp 17, ubiquitin conjugating enzyme E2T, and heat shock protein 70. IGF binding protein 5, stearyl-CoA desaturase, and annexin A1 were decreased. The differential regulation between Timp1 and Timp3 may correlate with their unique roles in the processes of ovulation and luteinization. For TIMP3, this may include regulating fatty acid synthesis, steroidogenesis, and protein turnover.

Ontogeny of MMPs and TIMPs in the murine neocortex

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) have been implicated in normal brain development, adult stroke, and, more recently, perinatal brain injury. Here, our objective was to obtain comprehensive and comparative data on the ontogeny of MMP-2, MMP-9, TIMP-1, and TIMP-2 in the neocortex of male and female mice belonging to various strains, from embryonic life to adulthood. We used gelatin zymography, ELISA, and real-time PCR analyses. MMP-2, MMP-9, and TIMP-1 activity and/or expression peaked during embryonic life and the early neonatal period, whereas TIMP-2 peaked during the first two postnatal weeks. Comparable results were obtained in all the mouse strains except BALB/c, where MMP-2 levels were considerably lower at all ages compared with the other strains. No gender effect was observed on any of the study parameters. This comprehensive study will serve as a basis for future investigations into the role for MMPs and TIMPs in normal brain development and prenatal brain injury.

Association of matrix metalloproteinases with MRI indices of brain ischemia and aging

Magnetic resonance imaging (MRI) findings of large white matter hyperintensities (LWMH), decreased brain volume and silent cerebral infarcts (SCI) are subclinical indices of brain ischemia and aging. Although the pathophysiology of these findings remains uncertain, extracellular matrix (ECM) remodeling, a process regulated by matrix metalloproteinases (MMPs) and their inhibitors (TIMPs), may be implicated. We evaluated the cross-sectional relations of circulating MMP-9 and TIMP-1 to these MRI indices in 583 stroke and dementia-free, Framingham Offspring participants (mean age 57 years, 58% women). Using multivariable regression MMP-9 (detectable versus non-detectable) and TIMP-1 (modeled as sex-specific quartiles) were related to LWMH (>1S.D. above age-specific mean; yes/no), SCI (yes/no) and total brain volume (ratio of parenchymal to intracranial volume, TCBVr). Mean TCBVr was 0.78 (S.D. 0.03), 13% of subjects had LWMH and 12% had SCI. Detectable MMP-9 was associated with higher prevalence of LWMH (OR 2.09, 95%confidence interval (CI) 1.00-4.37), but not with TCBVr. TIMP-1 was associated with a high prevalence of LWMH (OR for Q4 versus Q1-3: 1.83, 95%CI 1.06-3.18) and with lower mean TCBVr (Q4 associated with 0.17 S.D. units lower value relative to Q1-3; p=0.04). Neither biomarker was associated with SCI. Our findings are preliminary but if confirmed in further studies, suggest a pathophysiological role for the MMP/TIMP pathway in processes of brain ischemia and aging.

Vesicular trafficking and secretion of matrix metalloproteinases-2, -9 and tissue inhibitor of metalloproteinases-1 in neuronal cells

Matrix metalloproteinases (MMPs) are endopeptidases that cleave matrix, soluble and membrane-bound proteins and are regulated by their endogenous inhibitors the tissue inhibitors of MMPs (TIMPs). Nothing is known about MMP/TIMP trafficking and secretion in neuronal cells. We focussed our attention on the gelatinases MMP-2 and MMP-9, and their inhibitor TIMP-1. MMPs and TIMP-1 fused to GFP were expressed in N2a neuroblastoma and primary neuronal cells to study trafficking and secretion using real time video-microscopy, imaging, electron microscopy and biochemical approaches. We show that MMPs and TIMP-1 are secreted in 160-200 nm vesicles in a Golgi-dependent pathway. These vesicles distribute along microtubules and microfilaments, co-localise differentially with the molecular motors kinesin and myosin Va and undergo both anterograde and retrograde trafficking. MMP-9 retrograde transport involves the dynein/dynactin molecular motor. In hippocampal neurons, MMP-2 and MMP-9 vesicles are preferentially distributed in the somato-dendritic compartment and are found in dendritic spines. Non-transfected hippocampal neurons also demonstrate vesicular secretion of MMP-2 in both its pro- and active forms and gelatinolytic activity localised within dendritic spines. Our results show differential trafficking of MMP and TIMP-1-containing vesicles in neuronal cells and suggest that these vesicles could play a role in neuronal and synaptic plasticity.

Brain extracellular matrix in neurodegeneration

The role of extracellular matrix (ECM) in neurological development, function and degeneration has evolved from a simplistic physical adhesion to a system of intricate cellular signaling. While most cells require ECM adhesion to survive, it is now clear that differentiated function is intimately dependent upon cellular interaction with the ECM. Therefore, it is not surprising that the ECM is increasingly found to be involved in the enigmatic process of neurodegeneration. Descriptive studies of human neurodegenerative disorders and experimental studies of animal models of neurodegeneration have begun to define potential mechanisms of ECM disruption that can lead to synaptic and neuronal loss.

Tissue inhibitor of metalloproteinases-3 (TIMP-3) expression is increased during serum deprivation-induced neuronal apoptosis in vitro and in the G93A mouse model of amyotrophic lateral sclerosis: a potential modulator of Fas-mediated apoptosis

Cortical neurons deprived of serum undergo apoptosis that is sensitive to inhibitors of macromolecule synthesis. Proteomic analysis revealed differential expression of 49 proteins in cortical neurons 8 h after serum deprivation. Tissue inhibitor of metalloproteinases-3 (TIMP-3), a pro-apoptotic protein in various cancer cells, was increased during serum deprivation-induced apoptosis (SDIA), but not during necrosis induced by excitotoxicity or oxidative stress. Levels of TIMP-3 were markedly increased in degenerating motor neurons in a transgenic model of familial amyotrophic lateral sclerosis. The TIMP-3 expression was accompanied by increase in Fas-FADD interaction, activated caspase-8, and caspase-3 during SDIA and in vulnerable spinal cord of the ALS mouse. SDIA and activation of the Fas pathway were prevented by addition of an active MMP-3. Timp-3 deletion by RNA interference attenuated SDIA in N2a cells. These findings provide evidence that TIMP-3 is an upstream mediator of neuronal apoptosis and likely contributes to neuronal loss in neurodegenerative diseases such as amyotrophic lateral sclerosis.

Matrix metalloproteinases in brain development and remodeling: synaptic functions and targets

Matrix metalloproteinases (MMPs) play critical roles in egg fertilization, embryonic development, wound repair, cancer, and inflammatory and neurologic diseases. This subfamily of metzincin peptidases can cleave extracellular matrix (ECM) and pericellular proteins that have profound effects on cell behavior. Among known MMP substrates are several proteins that play important roles in synaptogenesis, synaptic plasticity, and long-term potentiation (LTP). In this Mini-Review we discuss how MMP-directed cleavage of these proteins can impact the formation and function of synapses within the brain. Pyramidal neurons in the hippocampus, and other large neurons, are surrounded by perineuronal nets that are composed of brevican, tenascin-R, and laminin, each of which is subject to proteolytic cleavage by MMPs. Tenascin-R knockout mice show deficits in learning and memory and LTP, as do at least two MMP knockouts. Impaired LTP is also seen in brain-derived neurotrophic factor (BDNF) knockout mice, which is interesting in that pro-BDNF can be processed into mature BDNF by several MMPs and thereby regulate activation of the high-affinity BDNF receptor TrkB. At the synaptic level, MMP substrates also include ephrins, Eph receptors, and cadherins, which are also involved in synapse development and plasticity. MMPs can also process membrane-bound tumor necrosis factor-alpha into a potent soluble cytokine that is increasingly implicated in neuron-glial signaling, particularly in neurologic disease. Finally, we discuss how the development of therapeutics to attenuate MMP activity in neurodegenerative disorders may become powerful tools for future studies of synaptic formation and function within the developing and mature brain.

Neuropsychotoxicity of abused drugs: involvement of matrix metalloproteinase-2 and -9 and tissue inhibitor of matrix metalloproteinase-2 in methamphetamine-induced behavioral sensitization and reward in rodents

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) function to remodel the pericellular environment. We have investigated the role of the MMP/TIMP system in methamphetamine (METH) dependence in rodents, in which the remodeling of neural circuits may be crucial. Repeated METH treatment induced behavioral sensitization, which was accompanied by an increase in MMP-2/-9/TIMP-2 activity in the brain. An antisense TIMP-2 oligonucleotide enhanced the sensitization, which was associated with a potentiation of the METH-induced release of dopamine in the nucleus accumbens (NAc). MMP-2/-9 inhibitors blocked the METH-induced behavioral sensitization and conditioned place preference (CPP), a measure of the rewarding effect of a drug, and reduced the METH-increased dopamine release in the NAc. In MMP-2- and MMP-9-deficient mice, METH-induced behavioral sensitization and CPP as well as dopamine release were attenuated. The MMP/TIMP system may be involved in METH-induced sensitization and reward by regulating extracellular dopamine levels.

The multiple sclerosis degradome: enzymatic cascades in development and progression of central nervous system inflammatory disease

An array of studies implicate different classes of protease and their endogenous inhibitors in multiple sclerosis (MS) pathogenesis based on expression patterns in MS lesions, sera, and/or cerebrospinal fluid (CSF). Growing evidence exists regarding their mechanistic roles in inflammatory and neurodegenerative aspects of this disease. Proteolytic events participate in demyelination, axon injury, apoptosis, and development of the inflammatory response including immune cell activation and extravasation, cytokine and chemokine activation/inactivation, complement activation, and epitope spreading. The potential significance of proteolytic activity to MS therefore relates not only to their potential use as important biomarkers of disease activity, but additionally as prospective therapeutic targets. Experimental data indicate that understanding the net physiological consequence of altered protease levels in MS development and progression necessitates understanding protease activity in the context of substrates, endogenous inhibitors, and proteolytic cascade interactions, which together make up the MS degradome. This review will focus on evidence regarding the potential physiologic role of those protease families already identified as markers of disease activity in MS; that is, the metallo-, serine, and cysteine proteases.

Gene expression profile analysis of epilepsy-associated gangliogliomas

Gangliogliomas (GG) constitute the most frequent tumor entity in young patients undergoing surgery for intractable epilepsy. The histological composition of GG, with the presence of dysplastic neurons, corroborates their maldevelopmental origin. However, their histogenesis, the pathogenetic relationship with other developmental lesions, and the molecular alterations underlying the epileptogenicity of these tumors remain largely unknown. We performed gene expression analysis using the Affymetrix Gene Chip System (U133 plus 2.0 array). We used GENMAPP and the Gene Ontology database to identify global trends in gene expression data. Our analysis has identified various interesting genes and processes that are differentially expressed in GG when compared with normal tissue. The immune and inflammatory responses were the most prominent processes expressed in GG. Several genes involved in the complement pathway displayed a high level of expression compared with control expression levels. Higher expression was also observed for genes involved in cell adhesion, extracellular matrix and proliferation processes. We observed differential expression of genes as cyclin D1 and cyclin-dependent kinases, essential for neuronal cell cycle regulation and differentiation. Synaptic transmission, including GABA receptor signaling was an under-expressed process compared with control tissue. These data provide some suggestions for the molecular pathogenesis of GG. Furthermore, they indicate possible targets that may be investigated in order to dissect the mechanisms of epileptogenesis and possibly counteract the epileptogenic process in these developmental lesions.

Intracerebroventricular administration of an endothelin ETB receptor agonist increases expression of tissue inhibitor of matrix metalloproteinase-1 and -3 in rat brain

Production of tissue inhibitors of matrix metalloproteinases (TIMPs), a family of secreted proteins with inhibitory actions on matrix metalloproteinases (MMPs), is up-regulated following nerve injuries and is suggested to have protective effects against MMP-mediated tissue damages. To clarify the extracellular signals involved in TIMP production in the brain, the effects of endothelins (ETs), a family of vasoconstricting peptides, were examined. I.c.v. administration of 500 pmol/day Ala(1,3,11,15)-ET-1, an ET(B) receptor agonist, increased the level of TIMP-1 mRNA in rat hippocampus, caudate-putamen and cerebrum. Ala(1,3,11,15)-ET-1 increased the level of TIMP-3 mRNA in the cerebrum, but not in the hippocampus or caudate-putamen. TIMP-2 mRNA was not affected in these brain regions. Ala(1,3,11,15)-ET-1 also stimulated the production of TIMP-1 and TIMP-3 proteins in the cerebrum. Immunohistochemical observations in the hippocampi of Ala(1,3,11,15)-ET-1-infused rats showed that NeuN-positive neurons and glial fibrillary acidic protein-positive astrocytes were immunoreactive for TIMP-1. In the cerebrum, astrocytes had TIMP-1 and TIMP3 reactivity, but neurons did not. In rat cultured astrocytes, both 100 nM Ala(1,3,11,15)-ET-1 and ET-1 increased the mRNA levels and protein release of TIMP-1 and TIMP-3 mRNAs. The effects of ET-1 on astrocytic TIMP-1 and TIMP-3 mRNAs were inhibited by BQ788, an ET(B) antagonist. These findings indicate that activation of brain ET(B) receptors causes production of TIMP-1 and TIMP-3, and suggest the involvement of astrocytes in ET-induced TIMP production.

The matrix metalloproteinases and CNS plasticity: an overview

The matrix metalloproteinases (MMPs) are expressed in response to pro-inflammatory stimuli and other triggers. The MMPs cleave numerous substrates including extracellular matrix components, cytokines and growth factors. In the CNS, while most studied in the context of disease, the many physiological functions of the MMPs are now becoming appreciated. This review provides an overview of the growing body of evidence for physiological roles of MMPs both in CNS development and in CNS plasticity in normal brain functioning, including learning and memory, as well as in CNS repair and reorganization as part of the neuroimmune response to injury.

In vivo roles for matrix metalloproteinase-9 in mature hippocampal synaptic physiology and plasticity

Extracellular proteolysis is an important regulatory nexus for coordinating synaptic functional and structural plasticity, but the identity of such proteases is incompletely understood. Matrix metalloproteinases (MMPs) have well-known, mostly deleterious roles in remodeling after injury or stroke, but their role in nonpathological synaptic plasticity and function in intact adult brains has not been extensively investigated. Here we address the role of MMP-9 in hippocampal synaptic plasticity using both gain- and loss-of-function approaches in urethane-anesthetized adult rats. Acute blockade of MMP-9 proteolytic activity with inhibitors or neutralizing antibodies impairs maintenance, but not induction, of long-term potentiation (LTP) at synapses formed between Schaffer-collaterals and area CA1 dendrites. LTP is associated with significant increases in levels of MMP-9 and proteolytic activity within the potentiated neuropil. By introducing a novel application of gelatin-substrate zymography in vivo, we find that LTP is associated with significantly elevated numbers of gelatinolytic puncta in the potentiated neuropil that codistribute with immunolabeling for MMP-9 and for markers of synapses and dendrites. Such increases in proteolytic activity require NMDA receptor activation. Exposing intact area CA1 neurons to recombinant-active MMP-9 induces a slow synaptic potentiation that mutually occludes, and is occluded by, tetanically evoked potentiation. Taken together, our data reveal novel roles for MMP-mediated proteolysis in regulating nonpathological synaptic function and plasticity in mature hippocampus.

Role of matrix metalloproteinase and tissue inhibitor of MMP in methamphetamine-induced behavioral sensitization and reward: implications for dopamine receptor down-regulation and dopamine release

Matrix metalloproteinases (MMPs) and its inhibitors (TIMPs) function to remodel the pericellular environment. We have demonstrated that methamphetamine (METH)-induced behavioral sensitization and reward were markedly attenuated in MMP-2- and MMP-9 deficient [MMP-2-(-/-) and MMP-9-(-/-)] mice compared with those in wild-type mice, suggesting that METH-induced expression of MMP-2 and MMP-9 in the brain plays a role in the development of METH-induced sensitization and reward. In the present study, we investigated the changes in TIMP-2 expression in the brain after repeated METH treatment. Furthermore, we studied a role of MMP/TIMP system in METH-induced behavioral changes and dopamine neurotransmission. Repeated METH treatment induced behavioral sensitization, which was accompanied by an increase in TIMP-2 expression. Antisense TIMP-2 oligonucleotide (TIMP-AS) treatment enhanced the sensitization, which was associated with the potentiation of METH-induced dopamine release in the nucleus accumbens (NAc). On the other hand, MMP-2/-9 inhibitors blocked the METH-induced behavioral sensitization and conditioned place preference, a measure of the rewarding effect, and reduced the METH-increased dopamine release in the NAc. Dopamine receptor agonist-stimulated [(35)S]GTPgammaS binding was reduced in the frontal cortex of sensitized rats. TIMP-AS treatment potentiated, while MMP-2/-9 inhibitor attenuated, the reduction of dopamine D2 receptor agonist-stimulated [(35)S]GTPgammaS binding. Repeated METH treatment also reduced dopamine D2 receptor agonist-stimulated [(35)S]GTPgammaS binding in wild-type mice, but such changes were significantly attenuated in MMP-2-(-/-) and MMP-9-(-/-) mice. These results suggest that the MMP/TIMP system is involved in METH-induced behavioral sensitization and reward, by regulating dopamine release and receptor signaling.

MMP-12, MMP-3, and TIMP-1 are markedly upregulated in chronic demyelinating theiler murine encephalomyelitis

Theiler murine encephalomyelitis (TME) represents a highly relevant viral model for multiple sclerosis. Matrix metalloproteinases (MMPs) degrade extracellular matrix molecules and are involved in demyelination processes. To elucidate their impact on demyelination in TME, spinal cords of TME virus (TMEV)-infected SJL/J mice were taken at 9 different time points postinfection (pi) ranging from 1 hour to 196 days pi and investigated for the expression of TMEV, MMP-2, -3, -7, -9, -10, -11, -12, -13, -14, -15, -24, and TIMP-1 to -4 by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). High TMEV RNA levels were detectable throughout the observation period using RT-qPCR. In addition, TMEV RNA was visualized within demyelinated lesions by in situ hybridization. MMP-3 mRNA was significantly upregulated at 1 day pi and again in the late phase of infection. TIMP-1 mRNA was significantly elevated throughout the observation period. MMP-12 mRNA was most prominently upregulated in the late phase of infection and MMP-12 protein was localized in intralesional microglia/macrophages and astrocytes by immunohistochemistry. In summary, in early TMEV infection, MMP-3 and TIMP-1 mRNA upregulation might be directly virus-induced, whereas persistent TMEV infection directly or indirectly stimulated MMP-12 production in microglia/macrophages and astrocytes and might account for ongoing demyelination in TME.

Activity-dependent release of precursor nerve growth factor, conversion to mature nerve growth factor, and its degradation by a protease cascade

In this report, we provide direct demonstration that the neurotrophin nerve growth factor (NGF) is released in the extracellular space in an activity-dependent manner in its precursor form (proNGF) and that it is in this compartment that its maturation and degradation takes place because of the coordinated release and the action of proenzymes and enzyme regulators. This converting protease cascade and its endogenous regulators (including tissue plasminogen activator, plasminogen, neuroserpin, precursor matrix metalloproteinase 9, and tissue inhibitor metalloproteinase 1) are colocalized in neurons of the cerebral cortex and released upon neuronal stimulation. We also provide evidence that this mechanism operates in in vivo conditions, as the CNS application of inhibitors of converting and degrading enzymes lead to dramatic alterations in the tissue levels of either precursor NGF or mature NGF. Pathological alterations of this cascade in the CNS might cause or contribute to a lack of proper neuronal trophic support in conditions such as cerebral ischemia, seizure and Alzheimer's disease or, conversely, to excessive local production of neurotrophins as reported in inflammatory arthritis pain.

Tissue inhibitors of metalloproteinases-1 (TIMP-1) and -2(TIMP-2) are major serum factors that stimulate the TIMP-1 gene in human gingival fibroblasts

We demonstrate in this study that both TIMP-1 and TIMP-2 are major serum factors that stimulate the induction of TIMP-1 mRNA in quiescent human gingival fibroblasts (Gin-1 cells) at mid-G1 (6-9 h after serum stimulation) of the cell cycle, but not that of TIMP-2. When we chased the secretion of both TIMP proteins into culture medium containing 10% FCS freed of both TIMPs, TIMP-2 secretion rose to the level in 10% FCS after 24 h, but TIMP-1 secretion remained at a fairly low level even after 3 days, thus reflecting a contrastive difference in the induction of both TIMP mRNAs. The stimulating activity of TIMP-1 on the expression of the TIMP-1 gene switched over to inhibitory activity, when the TIMP-1 concentration in the culture medium exceeded about 30 ng/ml. The depletion of TIMP-1 and TIMP-2 from FCS affected remarkably the induction of c-jun and c-fos mRNAs, but not that of c-ets-1 mRNA. TIMP-1 and TIMP-2-dependent expression of AP-1 protein was further demonstrated by using nuclear extracts of Gin-1 cells in an electrophoretic mobility shift assay.

Matrix metalloproteinases and their inhibitors in the developing mouse brain and spinal cord: a reverse transcription quantitative polymerase chain reaction study

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are essential for coordinated extracellular matrix turnover during central nervous system development. Reverse transcription quantitative polymerase chain reaction was employed to evaluate the mRNA expression of MMP-2, -3, -7, -9, -10, -11, -12, -13, -14, -15, and -24, and TIMP-1, -2, -3, and -4 in the prosencephalon, rhombencephalon, and spinal cord of 1- to 40-week-old mice. The molecular data were interpreted in the context of morphological observations. Significantly higher expression levels of MMP-2, -11, -13, -14, -15, and -24, and TIMP-1 and -3 were found in the brain and spinal cord 1 week after birth compared to later time points, while MMP-9 and TIMP-2 upregulation was restricted to the brain. This upregulation coincided with the maximal extension of the transient cerebellar external granular layer, a marker of neuronal progenitor proliferation and migration. MMP-12 was significantly upregulated at later time points and found to be positively correlated with myelination in the rhombencephalon and spinal cord. MMP-3, -7, and -10 mRNA expressions remained unchanged or were negligible. In summary, while most of the MMPs and TIMPs studied seem to be involved in cell proliferation and migration, MMP-12 might be decisive for myelination.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) modulates neuronal death, axonal plasticity, and learning and memory

The tissue inhibitor of metalloproteinases-1 (TIMP-1) belongs to a family of multifunctional proteins that inhibit matrix metalloproteinases (MMPs), but also regulate cell growth, proliferation, migration and apoptosis in non-nervous tissues. We had previously reported that kainate (KA)-mediated excitotoxic seizures induce the expression of TIMP-1 in resistant neurons and reactive astrocytes of the rat CNS, but the functional implications of these changes had not been elucidated. In the present work we used a targeted gene null mutation in mice to investigate in vivo the involvement of TIMP-1 in neuronal death and axonal sprouting following KA. We found no differences in seizure behaviour between the wild-type (WT) and the TIMP-1 knock-out (KO) mice, without any compensation by other TIMPs, at least at the mRNA level. However, the TIMP-1 KO mice were resistant to excitotoxicity and did not undergo the typical mossy fibre sprouting observed in WT mice. The lack of TIMP-1 paradoxically hampered the increase in the activity of MMPs observed in the seizing WT mice. In addition, we demonstrate that learning and memory are impaired in untreated KO mice. In conclusion, this study provides the first in vivo evidence for the implication of TIMP-1 in neuronal death and axonal sprouting in a pathological situation, but also suggests the involvement of TIMP-1 in the synaptic mechanisms underlying learning and memory in physiological conditions. More generally, these data support the idea that the control of proteolysis is instrumental for pathological and physiological processes in the brain.

Matrix metalloproteinase-2 (MMP-2) regulates astrocyte motility in connection with the actin cytoskeleton and integrins

Matrix Metalloproteinases (MMPs) play a role in migration of many cell types outside the central nervous system (CNS). Among neural cells, astrocytes are one of the main sources of MMPs in physiological and postlesional conditions. However, no data are available on the possible role of MMPs in astrocyte motility. Using an in vitro model of 2D migration and broad spectrum and selective MMP inhibitors, the authors demonstrated that MMP-2, but not MMP-9, is a key enzyme for astrocyte migration. In support of these data, the authors found constitutive expression of MMP-2 in astrocytes, while MMP-9 was nearly undetectable by gel zymography and immunocytochemical methods. The inhibition of migration by MMP inhibitors correlated with changes in cell morphology and in the organization of the actin cytoskeleton. In parallel, the characteristic focalized distribution of MMP-2 at the migration front observed in control cells became more diffuse and internalized by treatments that inhibited migration. The disruption of actin by cytochalasin D caused the partial recruitment of MMP-2 and gelatinolytic activity into actin aggregates, indicating a connection between the proteinase and the actin cytoskeleton. Finally, the authors found a co-localization of beta1-integrin with MMP-2 at the leading edge of migrating astrocytes. Altogether, these data provide the first evidence for the implication of MMP-2 in astrocyte motility, probably through the interaction of the proteinase with beta1-integrin that could act as a linker between pericellular proteolysis and the actin cytoskeleton.

Distribution and expression of tissue inhibitors of metalloproteinase in dorsal root entry zone and dorsal column after dorsal root injury

To understand whether tissue inhibitors of metalloproteinase (TIMPs) contribute to the failure of regenerating sensory axons to enter the spinal cord, we used in situ hybridization and immunocytochemistry to examine the expression of TIMP1, TIMP2, and TIMP3 in the dorsal root, dorsal root entry zone (DREZ), and dorsal column after dorsal root injury in adult rats. We found that the three TIMPs and their mRNAs were up-regulated in a time-, region-, and cell-type-specific manner. Strong up-regulation of all three TIMPs was seen in the injured dorsal roots. TIMP2 was also significantly up-regulated in the DREZ and degenerating dorsal column, where TIMP1 and TIMP3 showed only moderate up-regulation. Most cells up-regulating the TIMPs in the DREZ and degenerating dorsal column were reactive astrocytes, but TIMP2 was also up-regulated by microglia/macrophages, especially at long postoperative survival times. These results suggest that TIMPs may be involved in controlling tissue remodelling following dorsal root injury and that manipulation of the expression of TIMPs may provide a means of promoting axonal regeneration into and within the injured spinal cord.

Astrocyte reactivity to Fas activation is attenuated in TIMP-1 deficient mice, an in vitro study

Background

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a multifunctional secreted protein with pleiotropic actions, including the inhibition of matrix metalloproteinases (MMPs), cell death/survival and growth promoting activities. After inflammatory challenge, the levels of TIMP-1 are highly and selectively upregulated in astrocytes among glial cells, but little is know about its role in these neural cells. We investigated the influence of TIMP-1 null mutation in the reactivity of cultured astrocytes to pro-inflammatory stimuli with TNF-α and anti-Fas antibody.

Results

When compared to WT, mutant astrocytes displayed an overall increased constitutive gelatinase expression and were less responsive to Fas-mediated upregulation of MMP-9, of monocyte chemoattractant protein-1 (MCP-1) and of intercellular cell adhesion molecule-1 (ICAM-1), all markers of astrocyte inflammatory response. In contrast, TNF-α treatment induced all these factors similarly regardless of the astrocyte genotype. The incorporation of ³H-thymidin, a marker of cell proliferation, increased in wild-type (WT) astrocytes after treatment with anti-Fas antibody or recombinant TIMP-1 but not in mutant astrocytes. Finally, lymphocyte chemotaxis was differentially regulated by TNF-α in WT and TIMP-1 deficient astrocytes.

Conclusion

We provide evidence that the alteration of the MMP/TIMP balance in astrocytes influences their reactivity to pro-inflammatory stimuli and that Fas activation modulates the expression of members of the MMP/TIMP axis. We hypothesise that the Fas/FasL transduction pathway and the MMP/TIMP system interact in astrocytes to modulate their inflammatory response to environmental stimuli.

Gene profiling the response to kainic acid induced seizures

Kainic acid activates non-N-methyl-d-aspartate (NMDA) glutamate receptors where it increases synaptic activity resulting in seizures, neurodegeneration, and remodeling. We performed microarray analysis on rat hippocampal tissue following kainic acid treatment in order to study the signaling mechanisms underlying these diverse processes in an attempt to increase our current understanding of mechanisms contributing to such fundamental processes as neuronal protection and neuronal plasticity. The kainic acid-treated rats used in our array experiments demonstrated severe seizure behavior that was also accompanied by neuronal degeneration which is suggested by fluoro-jade B staining and anti-caspase-3 immunohistochemistry. The gene profile revealed 36 novel kainic acid regulated genes along with additional genes previously reported. The functional roles of these novel genes are discussed. These genes mainly have roles in transcription and to a lesser extent have roles in cell death, extracellular matrix remodeling, cell cycle progression, neuroprotection, angiogenesis, and synaptic signaling. Gene regulation was confirmed via quantitative real time polymerase chain reaction and in situ hybridization.

Spatio-temporal expression of immediate early genes in the central nervous system of SJL/J mice

Gene products of immediate early genes (IEGs) interact with specific binding sites in promoter regions of inducible and constitutively expressed genes. Thereby, they control transcription of down-stream targets, like pro- and anti-apoptotic genes and matrix-metalloproteinases (MMPs), known to play an important role in development, plasticity, response to injury and repair of the central nervous system (CNS). A real-time quantitative RT-PCR and immunohistochemical investigation was performed to study mRNA expression levels and protein distribution patterns of IEGs in cerebrum, cerebellum, and spinal cord of SJL/J mice between postnatal weeks 1 and 40. A down-regulation of c-jun, NF-kappaB1, Max, Ets-1, and p53 mRNA, and an up-regulation of c-fos mRNA was noticed. Down-regulations of Ets-1 and p53 were most prominent between week 1 and 3. The prominent role in CNS development for c-jun, Ets-1 and Max was supported by immunohistochemistry. One-week-old mice were strongly positive for all three proteins in cerebral cortex, medulla oblongata, and gray matter of the spinal cord. A high staining intensity was detected in the developing granule cell layer of the cerebellum for c-jun and Ets-1, and in the Purkinje cell layer of the cerebellum for Max. In addition to the general down-regulation of most mRNAs, minor up-regulations of all IEG proteins could be detected in restricted parts of the CNS indicating regional variations and differential expression and translation during development. Apoptosis was demonstrated using immunohistochemistry for active caspase-3. The expression patterns of IEGs might represent the key to understand the balance of proteolytic activities by MMPs, myelination, and the induction of apoptosis during the development of the CNS.

The potential use of MMP inhibitors to treat CNS diseases

The matrix metalloproteinases (MMPs) are considered to be the physiological mediators of extracellular matrix remodelling. MMPs are involved in a variety of functions and in the nervous system, these include angiogenesis and the extension of neuronal growth cones during development. However, it has become increasingly evident that the aberrant expression of MMPs in the nervous system contributes to diseases that include among others, multiple sclerosis, malignant gliomas, Alzheimer's disease and stroke. This review highlights the evidence that MMPs are involved in diseases of the nervous system, and provides information for the potential beneficial use of MMP inhibitors in NS disorders. However, the application of MMP inhibitors to treat CNS diseases must be balanced carefully against the beneficial roles normally played by MMPs in CNS physiology or recovery.

The brain angiotensin system and extracellular matrix molecules in neural plasticity, learning, and memory

The brain renin-angiotensin system (RAS) has long been known to regulate several classic physiologies including blood pressure, sodium and water balance, cyclicity of reproductive hormones and sexual behaviors, and pituitary gland hormones. These physiologies are thought to be under the control of the angiotensin II (AngII)/AT1 receptor subtype system. The AT2 receptor subtype is expressed during fetal development and is less abundant in the adult. This receptor appears to oppose growth responses facilitated by the AT1 receptor, as well as growth factor receptors. Recent evidence points to an important contribution by the brain RAS to non-classic physiologies mediated by the newly discovered angiotensin IV (AngIV)/AT4 receptor subtype system. These physiologies include the regulation of blood flow, modulation of exploratory behavior, and a facilitory role in learning and memory acquisition. This system appears to interact with brain matrix metalloproteinases in order to modify extracellular matrix molecules thus permitting the synaptic remodeling critical to the neural plasticity presumed to underlie memory consolidation, reconsolidation, and retrieval. There is support for an inhibitory influence by AngII activation of the AT1 subtype, and a facilitory role by AngIV activation of the AT4 subtype, on neuronal firing rate, long-term potentiation, associative and spatial learning. The discovery of the AT4 receptor subtype, and its facilitory influence upon learning and memory, suggest an important role for the brain RAS in normal cognitive processing and perhaps in the treatment of dysfunctional memory disease states.

Matrix metalloproteinases and their endogenous inhibitors in neuronal physiology of the adult brain

More than 20 matrix metalloproteinases (MMPs) and four of their endogenous tissue inhibitors (TIMPs) act together to control tightly temporally restricted, focal proteolysis of extracellular matrix. In the neurons of the adult brain several components of the TIMP/MMP system are expressed and are responsive to changes in neuronal activity. Furthermore, functional studies, especially involving blocking of MMP activities, along with the identification of MMP substrates in the brain strongly suggest that this enzymatic system plays an important physiological role in adult brain neurons, possibly being pivotal for neuronal plasticity.

The TIMPs tango with MMPs and more in the central nervous system

The matrix metalloproteinases (MMPs) are a family of zinc-dependent extracellular proteases that have been implicated in CNS development and disease. Crucial homeostatic regulation of MMPs is mediated through the expression and actions of the tissue inhibitors of metalloproteinases (TIMPs). Although the TIMPs are recognized inhibitors of the MMPs, recent studies have revealed that these proteins also can exhibit biological activities that are distinct from their interactions with or inhibition of the MMPs. With our understanding of the roles of the TIMPs in the CNS continuously emerging, this review examines the current state of knowledge regarding the multifarious and novel functions of this family of proteins, with particular attention to their increasing potential in the development, plasticity, and pathology of the CNS.

Tissue inhibitor of metalloproteinase (TIMP)-1: the TIMPed balance of matrix metalloproteinases in the central nervous system

Astrocytes are intimately involved in the mechanisms of neural injury and repair. They participate in a variety of homeostatic functions and elicit repair responses as balance mechanisms. Currently, there is a growing appreciation of a more active role of astrocytes in neuronal signaling and function. One key homeostatic mechanism of astrocytes in tissue repair is maintained through their production of tissue inhibitors of metalloproteinases (TIMPs). The family of TIMPs (1-4) plays a central regulatory role as inhibitors of matrix metalloproteinases (MMPs), enzymes involved in extracellular matrix maintenance and remodeling. Recently, TIMP-1, the inducible form, has been identified as a multifunctional molecule with divergent functions. It participates in wound healing and regeneration, cell morphology and survival, tumor metastasis, angiogenesis, and inflammatory responses. An imbalance of MMP/TIMP regulation has been implicated in several inflammatory diseases of the central nervous system (CNS). Here we review the conundrums of TIMP-1 regulation in CNS pathophysiology. We propose that astrocyte-TIMP-1 may play an important role in CNS homeostasis and disease. Astrocyte TIMP-1 expression is differentially regulated in inflammatory neurodegenerative diseases and may have significant therapeutic relevance.

Correlated stage- and subfield-associated hippocampal gene expression patterns in experimental and human temporal lobe epilepsy

Epileptic activity evokes profound alterations of hippocampal organization and function. Genomic responses may reflect immediate consequences of excitatory stimulation as well as sustained molecular processes related to neuronal plasticity and structural remodeling. Using oligonucleotide microarrays with 8799 sequences, we determined subregional gene expression profiles in rats subjected to pilocarpine-induced epilepsy (U34A arrays, Affymetrix, Santa Clara, CA, USA; P < 0.05, twofold change, n = 3 per stage). Patterns of gene expression corresponded to distinct stages of epilepsy development. The highest number of differentially expressed genes (dentate gyrus, approx. 400 genes and CA1, approx. 700 genes) was observed 3 days after status epilepticus. The majority of up-regulated genes was associated with mechanisms of cellular stress and injury - 14 days after status epilepticus, numerous transcription factors and genes linked to cytoskeletal and synaptic reorganization were differentially expressed and, in the stage of chronic spontaneous seizures, distinct changes were observed in the transcription of genes involved in various neurotransmission pathways and between animals with low vs. high seizure frequency. A number of genes (n = 18) differentially expressed during the chronic epileptic stage showed corresponding expression patterns in hippocampal subfields of patients with pharmacoresistant temporal lobe epilepsy (n = 5 temporal lobe epilepsy patients; U133A microarrays, Affymetrix; covering 22284 human sequences). These data provide novel insights into the molecular mechanisms of epileptogenesis and seizure-associated cellular and structural remodeling of the hippocampus.

Le système MMP/TIMP dans le système nerveux

The matrix metalloproteinases (MMP) belong to a growing family of secreted or membrane-bound (MT-MMP) enzymes that cleave protein components of the extracellular matrix and bioactive factors involved in intercellular signaling. MMP activity is counterbalanced by their four physiological inhibitors, the tissue inhibitors of MMP (TIMPs). Together, MMP and TIMP control cell-cell and cell-matrix interactions associated with physiological processes. However, the breakdown of the protease-inhibitor balance may lead to the loss of tissue homeostasis and the development of degenerative and tumorigenic processes in various tissues. The emerging idea is that the MMP/TIMP system also plays a major role in the pathology and physiology of the nervous system and that mastering MMP activity will set the basis for new and more efficient therapeutic strategies against nervous system disorders.

Expression profiling in tuberous sclerosis complex (TSC) knockout mouse astrocytes to characterize human TSC brain pathology

Individuals with tuberous sclerosis complex (TSC) exhibit a variety of neurologic abnormalities, including mental retardation, epilepsy, and autism. Examination of human TSC brains demonstrate dysplastic astrocytes and neurons, areas of abnormal neuronal migration (tubers), and hamartomatous growths, termed subependymal nodules, which can progress to subependymal giant cell astrocytomas (SEGA). Previous studies have suggested that these neuropathologic features may result from abnormal neuroglial cell differentiation. In an effort to provide support for this hypothesis and to identify specific markers of aberrant neuroglial cell differentiation in TSC, we employed gene expression profiling on Tsc1 conditional knockout (Tsc1(GFAP)CKO) mouse astrocytes. We identified several transcripts implicated in central nervous system development that are differentially expressed in Tsc1(-/-) astrocytes compared to wild-type astrocytes. We validated the differential expression of select transcripts on the protein level both in primary cultures of Tsc1(-/-) astrocytes and in Tsc1(GFAP)CKO mouse brains. Moreover, we show that these markers are also differentially expressed within cortical tubers, but not in adjacent normal tissue from TSC patient brains. This study provides supportive evidence for a developmental defect in neuroglial cell differentiation relevant to the genesis of TSC nervous system pathology and underscores the utility of mouse modeling for understanding the molecular pathogenesis of human disease.

Integrins, synaptic plasticity and epileptogenesis

A number of processes are thought to contribute to the development of epilepsy including enduring increases in excitatory synaptic transmission, changes in GABAergic inhibition, neuronal cell death and the development of aberrant innervation patterns in part arising from reactive axonal growth. Recent findings indicate that adhesion chemistries and, most particularly, activities of integrin class adhesion receptors play roles in each of these processes and thereby are likely to contribute significantly to the cell biology underlying epileptogenesis. As reviewed in this chapter, studies of long-term potentiation have shown that integrins are important for stabilizing activity-induced increases in synaptic strength and excitability. Other work has demonstrated that seizures, and in some instances subseizure neuronal activity, modulate the expression of integrins and their matrix ligands and the activities of proteases which regulate them both. These same adhesion proteins and proteases play critical roles in axonal growth and synaptogenesis including processes induced by seizure in adult brain. Together, these findings indicate that seizures activate integrin signaling and induce a turnover in adhesive contacts and that both processes contribute to lasting changes in circuit and synaptic function underlying epileptogenesis.

Gene profile of electroconvulsive seizures: induction of neurotrophic and angiogenic factors

Electroconvulsive seizure therapy (ECS) is a clinically proven treatment for depression and is often effective even in patients resistant to chemical antidepressants. However, the molecular mechanisms underlying the therapeutic efficacy of ECS are not fully understood. One theory that has gained attention is that ECS and other antidepressants increase the expression of select neurotrophic factors that could reverse or block the atrophy and cell loss resulting from stress and depression. To further address this topic, we examined the expression of other neurotrophic-growth factors and related signaling pathways in the hippocampus in response to ECS using a custom growth factor microarray chip. We report the regulation of several genes that are involved in growth factor and angiogenic-endothelial signaling, including neuritin, stem cell factor, vascular endothelial growth factor (VEGF), VGF (nonacronymic), cyclooxygenase-2, and tissue inhibitor of matrix metalloproteinase-1. Some of these, as well as other growth factors identified, including VEGF, basic fibroblast growth factor, and brain-derived neurotrophic factor, have roles in mediating neurogenesis and cell proliferation in the adult brain. We also examined gene expression in the choroid plexus and found several growth factors that are enriched in this vascular tissue as well as regulated by ECS. These data suggest that an amplification of growth factor signaling combined with angiogenic mechanisms could have an important role in the molecular action of ECS. This study demonstrates the applicability of custom-focused microarray technology in addressing hypothesis-driven questions regarding the action of antidepressants.

Regulation of tissue inhibitor of metalloproteinase-1 by astrocytes: links to HIV-1 dementia

The neuropathogenesis of HIV-1-associated dementia (HAD) revolves around the secretion of toxic molecules from infected and immune-competent mononuclear phagocytes. Astrocyte activation occurs in parallel but limited insights are available for its role in neurotoxicity and cognitive dysfunction. One means in which astrocytes may affect disease is through their production of tissue inhibitors of metalloproteinases (TIMPs). TIMPs are regulators of matrix metalloproteinases, enzymes that affect blood-brain barrier integrity through altering the extracellular matrix. We hypothesized that in response to injury and inflammation in HAD, astrocytes regulate the production of TIMP-1, the inducible type of TIMP that is important in inflammation. To address astrocyte-mediated TIMP-1 regulation in HAD, we evaluated the responses of primary human to IL-1beta and HIV-1. TIMP-1 levels in plasma, CSF, and brain tissue of control, HIV-1 infected patients without cognitive impairment, and HAD patients were also studied. Our data show that an upregulation of TIMP-1 results from astrocytes acutely activated with IL-1beta. In contrast, CSF and brain tissue samples from HAD patients showed reduced TIMP-1 levels compared to seronegative controls. MMP-2 levels in brains showed the opposite. Consistent with this, prolonged activation of astrocytes led to a reduction in TIMP-1 and MMP-2, but a sustained elevation in MMP-1. Our data suggest that in diseased brain tissue, the ability of astrocytes to counteract the destructive effects of MMP through expression of TIMP-1 is diminished by chronic activation. Our studies reveal new opportunities for repair-based therapeutic strategies in HAD.

Increases in matrix metalloproteinase-9 and tissue inhibitor of matrix metalloproteinase-1 mRNA after cerebral contusion and depolarisation

Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) play major roles in physiological extracellular matrix turnover during normal development and in pathological processes. In brain, increases in MMP activity occur, for example, in multiple sclerosis, Alzheimer's disease, and after head trauma. We examined MMP-9 and TIMP-1, -2, and -3 in events after head trauma. A time-course study was carried out using two different rat injury models, cerebral contusion and depolarisation. Brains were analysed by RT-PCR and in situ hybridisation. We observed a distinct and time-dependent upregulation of MMP-9 and TIMP-1 mRNA in ipsilateral cortical areas. MMP-9 mRNA levels were upregulated 1 day after cerebral contusion with a peak at Day 4. Depolarisation per se, which also occurs after traumatic brain injury, lead to delayed increase of MMP-9 mRNA, 4 days post application. At Day 14, MMP-9 mRNA levels were indistinguishable from controls in both models. TIMP-1 mRNA increases were observed in both models 4 hr after injury, and increased further at Days 1 and 4. At Day 14, mRNA levels declined and were no higher than control levels. No alterations in mRNA levels were noted for TIMP-2 or -3. Our results support earlier reports on MMP-9 involvement in brain injury. It also shows a role for TIMP-1 in the mechanisms of trauma, where depolarisation could be the mechanism responsible for this upregulation.

Neuronal activity-dependent increase of net matrix metalloproteinase activity is associated with MMP-9 neurotoxicity after kainate

Matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs) are emerging as important modulators of brain physiopathology. Dramatic changes in the expression of MMPs and TIMPs occur during excitotoxic/neuroinflammatory processes. However, only the measurement of net protease activity is relevant physiologically, and the functional consequences of MMP/TIMP ratio modifications in the brain remain elusive. In order to assess MMP activity and effects in brain tissue, we combined in vivo and organotypic culture models of kainate (KA)-induced excitotoxicity to provoke selective neuronal death and neuroinflammation in the hippocampus. Using in situ zymography, we show that KA-induced excitotoxic seizures in rats increase net MMP activity in hippocampal neurons 8 h after seizures, before their death, and that this increase is neuronal activity-dependent. Three days after KA, proteolytic activity increases in blood vessels and reactive glial cells of vulnerable areas, in relation with neuroinflammation. At 7 and 15 days, proteolysis remains high in blood vessels whereas it is reduced in glia. In organotypic hippocampal cultures, which lack blood cell-mediated inflammation and extrinsic connections, a broad-spectrum inhibitor of MMPs (MMPI), but also a selective MMP-9 inhibitor, protect hippocampal neurons against KA-induced excitotoxicity. Moreover, recombinant MMP-9, but not MMP-2, induces selective pyramidal cell death in these cultures and KA-induced neuronal activity exacerbates the neuronal death promoting effects of MMP-9. These data strongly implicate MMPs, and MMP-9 in particular, in both excitotoxic neuronal damage and subsequent neuroinflammatory processes, and suggest that selective MMPIs could be therapeutically relevant in related neurological disorders.

Tissue inhibitors of matrix metalloproteinases are elevated in cerebrospinal fluid of neurodegenerative diseases

Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of diseases such as Alzheimer's Disease (AD) and amyotrophic lateral sclerosis (ALS). Increased expression of MMP-9 and TIMPs has been reported in postmortem AD and ALS brain tissue, as well as in ALS cerebrospinal fluid (CSF) and plasma. Although individual studies of MMP and TIMP expression in CSF have included AD and ALS samples, there are no studies comparing the expression of these proteins between neurodegenerative diseases. We measured the levels of matrix metalloproteinases (MMPs)-2 and -9 and the tissue inhibitor of MMPs (e.g. TIMP-1 and TIMP-2) in CSF samples from patients with Parkinson's Disease (PD), Huntington's Disease (HD), AD and ALS as compared to age-matched control patients. There was constitutive expression of the proform of gelatinase A (proMMP-2) on zymography gels in all CSF samples. Unexpectedly, there was an additional gelatinolytic band at 130 kDa of unknown etiology in the CSF samples of patients with PD (61% of patients studied), AD (61%), HD (25%) and ALS (39%). Levels of TIMP-1 were significantly elevated in CSF samples from all disease groups. TIMP-2 was significantly increased in CSF of AD and HD patients. MMP-2 levels did not differ significantly between groups. These findings show that TIMPs are elevated in the CSF of patients with neurodegenerative diseases suggesting a potential role of these endogenous inhibitors of matrix metalloproteinases in neurodegenerative diseases.

Tissue inhibitor of metalloproteinase 1 inhibits excitotoxic cell death in neurons

The upregulation of TIMP-1 following an excitotoxic injury has recently been hypothesized to be part of a general neuronal response that mediates long-lasting changes involved in tissue reorganization and possibly neuroprotection. In this study we have shown for the first time that within hours of applying TIMP-1 in recombinant form or by adenovirus-mediated gene transfer, neurons are highly protected against excitotoxic injury. Neither TIMP-3 nor a nonsecretable form of TIMP-1 protected neurons. TIMP-1 conferred highly significant protection to hippocampal cells exposed to a wide range of glutamic acid concentrations in both dissociated and organotypic hippocampal cultures. TIMP-1 did not prevent apoptotic cell death or death mediated by chemical ischemia. The observed neuroprotection may be explained by a decrease in calcium influx into neurons following stimulation with glutamate. These findings have a fundamental implication for our understanding of the physiological role of secreted TIMP-1 in the central nervous system.

Glycosaminoglycan levels and proteoglycan expression are altered in the hippocampus of patients with mesial temporal lobe epilepsy

Extracellular matrix proteoglycans (PGs) and glycosaminoglycans (GAGs) play a crucial role in cell differentiation and synaptogenesis by modulating neurite outgrowth. The chondroitin sulfate (CS)-rich PG, the receptor protein tyrosine phosphatase zeta/beta (RPTP zeta/beta), has been related to neural morphogenesis and axon guidance. Hippocampal sclerosis is the most frequent pathologic finding in patients with intractable mesial temporal lobe epilepsy (MTLE), which is associated with neuron loss, reactive gliosis, and mossy fiber sprouting. In the present study, we investigated the concentration of CS, heparan sulfate (HS) and hyaluronic acid (HA) in the hippocampus and temporal neocortex as well as RPTP zeta/beta expression in the hippocampus of patients with MTLE. Compared to autopsy control tissue, epileptic hippocampi showed a significantly increased concentration of CS (224%; p=0.0109) and HA (146%; p=0.039). HS was instead similar to control values. No differences were found in the concentration of CS, HS, or HA in the temporal neocortex of epileptic patients when compared to control values. In contrast, RPTP zeta/beta immunoreactivity was induced in astrocytes of the inner molecular layer of the dentate gyrus of the sclerotic hippocampus. Because matrix compounds have been associated with tissue injury and repair, the present findings suggest that changes in PGs and GAGs might be related to damage-induced gliosis and neuronal reorganization in the hippocampus of MTLE patients.

Expression of MMP-2, MMP-9, and MMP-1 and their endogenous counterregulators TIMP-1 and TIMP-2 in postmortem brain tissue of Parkinson's disease

We investigated the levels and tissue localization of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) in postmortem brain tissue from Parkinson's disease (PD) and age-matched control cases. Using zymography, we found reduced MMP-2 levels in PD cases in the substantia nigra as compared to controls; levels of MMP-2 were not significantly changed in the cortex and the hippocampus. MMP-9 levels were unchanged in the investigated brain regions. Immunohistochemically, MMP-2 was localized primarily in astrocytes and microglia cells, whereas MMP-9 was predominantly neuronal. Levels of TIMP-1, an endogenous tissue inhibitor of MMPs, were significantly elevated in the substantia nigra, but not in the cortex and hippocampus. TIMP-2 levels were unchanged in PD. To investigate whether increased TIMP-1 levels in the substantia nigra might be due to increased MMP-1 expression, we measured MMP-1 levels using Western blots. MMP-1 levels were unchanged in PD cases compared to controls. Together, these data show alterations of MMP-2 and TIMP-1 in the substantia nigra of PD, consistent with the possibility that alterations in MMPs/TIMPs may contribute to disease pathogenesis.

Genetic polymorphisms and cerebrospinal fluid levels of tissue inhibitor of metalloproteinases 1 in sporadic Alzheimer's disease

Tissue inhibitor of metalloproteinases 1 (TIMP-1) inhibits several proteinases including a disintegrin and metalloproteinase 10 (ADAM10), a major alpha-secretase that cleaves the beta-amyloid precursor protein within its amyloidogenic Abeta domain. The gene encoding TIMP-1 (TIMP 1) maps to the short arm of the X chromosome, in a region previously suggested as conferring genetic susceptibility for Alzheimer's disease (AD). To determine whether genetic variability of TIMP 1 contributes to the pathogenesis of AD, we analysed one single nucleotide polymorphism within TIMP 1 and one single nucleotide polymorphism in the 5'-untranslated region of TIMP 1 in patients with AD and control subjects from two independent and ethnically different populations. We did not observe any association between TIMP 1 genotypes and the diagnosis of AD in men or women. We also measured TIMP-1 protein levels in the cerebrospinal fluid of patients with AD, healthy control subjects, and patients with other neurological disorders. TIMP-1 levels were similar in all groups. In addition, no significant differences were observed after stratification for TIMP 1 genotypes. Our data show that neither genetic variability nor protein levels of TIMP-1 are associated with AD.

Matrix metalloproteases and their inhibitors are produced by overlapping populations of activated astrocytes

Matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) are involved in many cell migration phenomena and produced by many cell types, including neurons and glia. To assess their possible roles in brain injury and regeneration, we investigate their production by glial cells, after brain injury and in tissue culture, and we investigate whether they are capable of digesting known axon-inhibitory proteoglycans. To determine the action of MMPs, we incubated astrocyte conditioned medium with activated MMPs, then did western blots for several chondroitin sulphate proteoglycans. MMP-3 digested all five proteoglycans tested, whereas MMP-2 digested only two and MMP-9 none. To determine whether MMPs or TIMPs are produced by astrocytes in vitro, we tested both primary cultures and astrocyte cell lines by western blotting, and compared them with Schwann cells. All cultures produced at least some MMPs and TIMPs, with no obvious correlation with the ability of axons to grow on those cells. Both MMP-9 and TIMP-3 were regulated by various cytokines. To determine which cells produce MMPs and TIMPs after brain injury, we made lesions of adult rat cortex, and did immunohistochemistry. MMP-2 was seen to be induced in activated astrocytes through the whole thickness of the cortex but not deeper, but MMP-3 was not seen in the injured brain. TIMP-2 and TIMP-3 immunoreactivities were induced in activated astrocytes in deep cortex and the underlying white matter. In situ hybridisation confirmed induction of TIMP-2 in glia as well as neurons, but showed no expression of TIMP-4. These results show that both MMPs and TIMPs are produced by some astrocytes, but TIMP production is particularly strong, especially in deep cortex and white matter which is more inhibitory for axon regeneration. Conversely the MMPs produced may not be adequate to promote migration of cells and axons within the glial scar.

Matrix metalloproteinase-9 undergoes expression and activation during dendritic remodeling in adult hippocampus

Neurons of adult brain are able to remodel their synaptic connections in response to various stimuli. Modifications of the peridendritic environment, including the extracellular matrix, are likely to play a role during synapse remodeling. Proteolytic disassembly of ECM is a complex process using the regulated actions of specific extracellular proteinases. One of best-characterized families of matrix-modifying enzymes is the matrix metalloproteinase (MMP) family. Here, we describe changes in the expression and function of two well known MMPs, MMP-9 and MMP-2, in adult rat brain before and after systemic administration of the glutamate receptor agonist kainate. Kainate application results in enhanced synaptic transmission and seizures followed by selective tissue remodeling, primarily in hippocampal dentate gyrus. MMP-9 but not MMP-2 was highly expressed by neurons in normal adult rat brain. MMP-9 protein was localized in neuronal cell bodies and dendrites. Kainate upregulated the level of MMP-9 mRNA and protein within hours after drug administration. This was followed several hours later by MMP-9 enzymatic activation. Within hippocampus, MMP-9 mRNA and activity were increased selectively in dentate gyrus, including its dendritic layer. In addition, MMP-9 mRNA levels decreased in areas undergoing neuronal cell loss. This unique spatiotemporal pattern of MMP-9 expression suggests its involvement in activity-dependent remodeling of dendritic architecture with possible effects on synaptic physiology.

Gelatinase B and TIMP-1 are regulated in a cell- and time-dependent manner in association with neuronal death and glial reactivity after global forebrain ischemia

Matrix metalloproteinases (MMPs) belong to a large family of endopeptidases that regulate the pericellular environment through the cleavage of protein components of the extracellular matrix, membrane receptors and cytokines. MMP activity is controlled by the multifunctional tissue inhibitors of metalloproteinases (TIMPs). Proteases and their inhibitors are critically involved in developmental and pathological processes in numerous organs, including the brain. Global transient cerebral ischemia induces selective delayed neuronal death and neuroinflammation. We compared, in discrete vulnerable and resistant areas of the ischemic rat hippocampus, the kinetics and cellular distribution of gelatinase B and its principal inhibitor TIMP-1 and we assessed by in situ zymography, the net gelatinolytic activity at the cellular level. We show that gelatinases are expressed and active in neurons, suggesting that MMPs play a role in maintaining neural homeostasis. In the ischemic rat brain, expression and activity of gelatinase B, and expression of TIMP-1 are altered in a time-, region- and cell-dependent manner. Gelatinase B is induced first in reactive microglia and subsequently in reactive astrocytes. In situ, increases in gelatinase activity accompanied the progression of neuronal death and glial reactivity. Our results suggest that MMPs and TIMPs are involved in cell viability and tissue remodelling in the ischemic brain, and reinforces the idea that the MMP/TIMP system contributes both to neuronal demise and tissue repair in the context of glial reactivity.

Morbillivirus infection of the mouse central nervous system induces region-specific upregulation of MMPs and TIMPs correlated to inflammatory cytokine expression

Viral infection of the central nervous system (CNS) can result in perturbation of cell-to-cell communication involving the extracellular matrix (ECM). ECM integrity is maintained by a dynamic balance between the synthesis and proteolysis of its components, mainly as a result of the action of matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). An MMP/TIMP imbalance may be critical in triggering neurological disorders, in particular in virally induced neural disorders. In the present study, a mouse model of brain infection using a neurotropic strain of canine distemper virus (CDV) was used to study the effect of CNS infection on the MMP/TIMP balance and cytokine expression. CDV replicates almost exclusively in neurons and has a unique pattern of expression (cortex, hypothalamus, monoaminergic nuclei, hippocampus, and spinal cord). Here we show that although several mouse brain structures were infected, they exhibited a differential pattern in terms of MMP, TIMP, and cytokine expression, exemplified by (i) a large increase in pro-MMP9 levels, in particular in the hippocampus, which occurred mainly in neurons and was associated with in situ gelatinolytic activity, (ii) specific and significant upregulation of MT1-MMP mRNA expression in the cortex and hypothalamus, (iii) an MMP/TIMP imbalance, suggested by the upregulation of TIMP-1 mRNA in the cortex, hippocampus, and hypothalamus and of TIMP-3 mRNA in the cortex, and (iv) a concomitant region-specific large increase in expression of Th1-like cytokines, such as gamma interferon, tumor necrosis factor alpha, and interleukin 6 (IL-6), contrasting with weaker induction of Th2-like cytokines, such as IL-4 and IL-10. These data indicate that an MMP/TIMP imbalance in specific brain structures, which is tightly associated with a local inflammatory process as shown by the presence of immune infiltrating cells, differentially impairs CNS integrity and may contribute to the multiplicity of late neurological disorders observed in this viral mouse model.

Plasminogen activator inhibitor-2 (PAI-2) mRNA is localized in the accumbens nucleus of the mouse brain and is induced in specific brain sites after kainate excitation

Plasminogen activator inhibitor-2 (PAI-2) specifically inhibits plasminogen activators, extracellular fibrinolytic serine proteases that are also implicated in brain plasticity and toxicity. Primarily localized intracellularly, PAI-2 is thought to also counteract apoptosis mediated by a currently undefined intracellular protease. Here we localized PAI-2 mRNA through in situ hybridization in brain cryosections derived from normal adult mice or after kainate excitation. We found that in the normal brain PAI-2 mRNA was confined to an area within the accumbens nucleus shell. After kainate was injected (i.p.), PAI-2 mRNA was substantially and rapidly (within 2 h) induced in neuron-like cells primarily in layers II-III of the neocortex; the cingulate, piriform, entorhinal and perirhinal cortices; the olfactory bulb, nucleus and tubercle; in the accumbens nucleus, shell and core; throughout the caudate putamen and the amygdaloid complex; in the CA1 and CA3 areas of the hippocampus, and in the parasubiculum. These findings suggest that PAI-2 could play a role in the accumbens nucleus as well as in activity-related events associated with olfactory, striatal, and limbic structures.

Kainate-induced genes in the hippocampus: lessons from expression patterns

Kainate, the analog of the excitatory amino acid L-glutamate, upon binding to non-NMDA glutamate receptors, causes depolarization of neurons followed by severe status epilepticus, neurodegeneration, plasticity and gliosis. These events are best observed in hippocampus, the limbic structure implicated in learning and long-term memory formation. Neurons in all hippocampal structures undergo hyper-activation, however, whereas the cells in the CA subfields degenerate within 2--3 days following the application of kainate, the granule cells of the dentate gyrus are resistant to any form of neurodegeneration and even initiate new synaptic contacts. These physiological and histological changes are modulated by short-term and long-term alterations in gene expression. Perhaps close examination of the changing spatio-temporal patterns of mRNAs of various genes may help in generating a clearer picture of the molecular events leading to complex cognitive functions.

Differential spatial distribution and temporal regulation of tissue inhibitor of metalloproteinase mRNA expression during rat central nervous system development

The elucidation of the cellular and molecular mechanisms governing the maturation of the central nervous system (CNS) is rapidly emerging. Cell-cell and cell-matrix interactions play critical roles in all phases of developmental tissue remodeling. Throughout development, an intricate balance between extracellular matrix synthesis and degradation is preserved by the opposing actions of matrix metalloproteinases (MMPs) and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Although recent evidence suggests that TIMPs exert diverse cell biological functions distinct from their MMP-inhibitory activities, few studies have investigated MMP or TIMP expression during CNS development. The present report analyzes the mRNA expression of the four known TIMPs throughout the course of embryonic and postnatal rat CNS development. The results clearly demonstrate the unique spatial distribution and temporal regulation of TIMP expression and suggest a distinct role for each TIMP during CNS development.