The up-regulation of stromelysin-1 (MMP-3) in a spontaneously demyelinating transgenic mouse precedes onset of disease

Circulating Extracellular Vesicles Express Receptor Activator of Nuclear Factor κB Ligand and Other Molecules Informative of the Bone Metabolic Status of Mouse Models of Experimentally Induced Osteoporosis

Extracellular vesicles (EVs) are potent means of cell-to-cell communication. They are released in biological fluids, including blood, urine, and saliva, and can be exploited to identify new biomarkers of diseases. We hypothesized that EVs contain molecular cargos involved in bone metabolism, possibly mirroring biological differences between postmenopausal and disuse osteoporosis. We tested this hypothesis in primary murine osteoblasts subjected to steroid depletion or to unloading, and in the serum of animal models of osteoporosis induced by ovariectomy or hindlimb tail suspension. EVs were isolated by ultracentrifugation and analysed by transmission electron microscopy, cytofluorimetry, immunoblotting and RT-PCR. Large-scale analyses were performed by Real-Time arrays and Proteome Profiler™ Antibody arrays. Finally, precise titration of analytes was carried out by ELISA assay. In vitro, we confirmed an increased release of EVs enriched in surface RANKL by primary mouse osteoblasts subjected to steroid depletion or simulated microgravity compared to controls. In vivo, circulating EVs isolated from the sera of control female mice expressed RANKL along with other genes associated with bone metabolism. Serum EVs from ovariectomized or hindlimb tail-suspended mice showed distinct molecular profiles. They expressed RANKL with different kinetics, while transcriptomic and proteomic profiles uncovered unique molecular signatures that discriminated the two conditions, unveiling exclusive molecules expressed in time- and osteoporosis type-dependent manner. These results suggest that circulating EVs could represent a new tool for monitoring the onset and the progression of diverse types of the disease in mice, paving the way for their exploitation to diagnose human osteoporosis in liquid biopsies.

A new role for matrix metalloproteinase-3 in the NGF metabolic pathway: Proteolysis of mature NGF and sex-specific differences in the continuum of Alzheimer's pathology

Matrix metalloproteinase-3 (MMP-3) has been associated with risk of Alzheimer's disease (AD). In this study we introduce a novel role for MMP-3 in degrading nerve growth factor (NGF) in vivo and examine its mRNA and protein expression across the continuum of AD pathology. We provide evidence that MMP-3 participates in the degradation of mature NGF in vitro and in vivo and that it is secreted from the rat cerebral cortex in an activity-dependent manner. We show that cortical MMP-3 is upregulated in the McGill-R-Thy1-APP transgenic rat model of AD-like amyloidosis. A similar upregulation was found in AD and MCI brains as well as in cognitively normal individuals with elevated amyloid deposition. We also observed that frontal cortex MMP-3 protein levels are higher in males. MMP-3 protein correlated with more AD neuropathology, markers of NGF metabolism, and lower cognitive scores in males but not in females. These results suggest that MMP-3 upregulation in AD might contribute to NGF dysmetabolism, and therefore to cholinergic atrophy and cognitive deficits, in a sex-specific manner. MMP-3 should be further investigated as a biomarker candidate or as a therapeutic target in AD.

Dcf1 deficiency induces hypomyelination by activating Wnt signaling

Myelination is extremely important in achieving neural function. Hypomyelination causes a variety of neurological diseases. However, little is known about how hypomyelination occurs. Here we investigated the effect of dendritic cell factor 1(Dcf1) on myelination, using in vitro and in vivo models and found that Dcf1 is essential for normal myelination, motor coordination and balance. Lack of Dcf1 downregulated myelin-associated proteins, such as myelin basic protein (MBP), myelin associated glycoprotein (MAG), and 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) in the hippocampus and corpus callosum of Dcf1-null mice, as a result, the myelin sheath of these mice became thinner. Transmission electron microscopy revealed hypomyelination in Dcf1-deficient mice. Motor coordination and balance tests confirmed impaired neurological function in Dcf1-null mice. Gain-of-function analysis via In utero electroporation showed that hypomyelination could be rescued by re-expression of Dcf1 in Dcf1-null mouse brain. Dcf1-null mice exhibited a phenotype similar to that of cuprizone-induced demyelinated mice, thereby supporting the finding of hypomyelination caused by Dcf1 knockout. Mechanistically, we further revealed that insufficient Dcf1 leads to hyperactivation of the Wnt/β-catenin signaling pathway. Our work describes the role of Dcf1 in maintaining normal myelination, and this could help improve the current understanding of hypomyelination and its pathogenesis.

Matrix metalloproteinases shape the oligodendrocyte (niche) during development and upon demyelination

The oligodendrocyte lineage cell is crucial to proper brain function. During central nervous system development, oligodendrocyte progenitor cells (OPCs) migrate and proliferate to populate the entire brain and spinal cord, and subsequently differentiate into mature oligodendrocytes that wrap neuronal axons in an insulating myelin layer. When damage occurs to the myelin sheath, OPCs are activated and recruited to the demyelinated site, where they differentiate into oligodendrocytes that remyelinate the denuded axons. The process of OPC attraction and differentiation is influenced by a multitude of factors from the cell's niche. Matrix metalloproteinases (MMPs) are powerful and versatile enzymes that do not only degrade extracellular matrix proteins, but also cleave cell surface receptors, growth factors, signaling molecules, proteases and other precursor proteins, leading to their activation or degradation. MMPs are markedly upregulated during brain development and upon demyelinating injury, where their broad functions influence the behavior of neural progenitor cells (NPCs), OPCs and oligodendrocytes. In this review, we focus on the role of MMPs in (re)myelination. We will start out in the developing brain with describing the effects of MMPs on NPCs, OPCs and eventually oligodendrocytes. Then, we will outline their functions in oligodendrocyte process extension and developmental myelination. Finally, we will review their potential role in demyelination, describe their significance in remyelination and discuss the evidence for a role of MMPs in remyelination failure, focusing on multiple sclerosis. In conclusion, MMPs shape the oligodendrocyte (niche) both during development and upon demyelination, and thus are important players in directing the fate and behavior of oligodendrocyte lineage cells throughout their life cycle.

MMP-10 is Increased in Early Stage Diabetic Kidney Disease and can be Reduced by Renin-Angiotensin System Blockade

Matrix metalloproteinases have been implicated in diabetic microvascular complications. However, little is known about the pathophysiological links between MMP-10 and the renin-angiotensin system (RAS) in diabetic kidney disease (DKD). We tested the hypothesis that MMP-10 may be up-regulated in early stage DKD, and could be down-regulated by angiotensin II receptor blockade (telmisartan). Serum MMP-10 and TIMP-1 levels were measured in 268 type 2 diabetic subjects and 111 controls. Furthermore, histological and molecular analyses were performed to evaluate the renal expression of Mmp10 and Timp1 in a murine model of early type 2 DKD (db/db) after telmisartan treatment. MMP-10 (473 ± 274 pg/ml vs. 332 ± 151; p = 0.02) and TIMP-1 (573 ± 296 ng/ml vs. 375 ± 317; p < 0.001) levels were significantly increased in diabetic patients as compared to controls. An early increase in MMP-10 and TIMP-1 was observed and a further progressive elevation was found as DKD progressed to end-stage renal disease. Diabetic mice had 4-fold greater glomerular Mmp10 expression and significant albuminuria compared to wild-type, which was prevented by telmisartan. MMP-10 and TIMP-1 are increased from the early stages of type 2 diabetes. Prevention of MMP-10 upregulation observed in diabetic mice could be another protective mechanism of RAS blockade in DKD.

Liquefaction of the Brain following Stroke Shares a Similar Molecular and Morphological Profile with Atherosclerosis and Mediates Secondary Neurodegeneration in an Osteopontin-Dependent Mechanism

Here we used mouse models of heart and brain ischemia to compare the inflammatory response to ischemia in the heart, a protein rich organ, to the inflammatory response to ischemia in the brain, a lipid rich organ. We report that ischemia-induced inflammation resolves between one and four weeks in the heart compared to between eight and 24 weeks in the brain. Importantly, we discovered that a second burst of inflammation occurs in the brain between four and eight weeks following ischemia, which coincided with the appearance of cholesterol crystals within the infarct. This second wave shares a similar cellular and molecular profile with atherosclerosis and is characterized by high levels of osteopontin (OPN) and matrix metalloproteinases (MMPs). In order to test the role of OPN in areas of liquefactive necrosis, OPN^-/- mice were subjected to brain ischemia. We found that at seven weeks following stroke, the expression of pro-inflammatory proteins and MMPs was profoundly reduced in the infarct of the OPN^-/- mice, although the number of cholesterol crystals was increased. OPN^-/- mice exhibited faster recovery of motor function and a higher number of neuronal nuclei (NeuN) positive cells in the peri-infarct area at seven weeks following stroke. Based on these findings we propose that the brain liquefies after stroke because phagocytic cells in the infarct are unable to efficiently clear cholesterol rich myelin debris, and that this leads to the perpetuation of an OPN-dependent inflammatory response characterized by high levels of degradative enzymes.

Myelin Basic Protein Citrullination in Multiple Sclerosis: A Potential Therapeutic Target for the Pathology

Multiple sclerosis (MS) is a multifactorial demyelinating disease characterized by neurodegenerative events and autoimmune response against myelin component. Citrullination or deimination, a post-translational modification of protein-bound arginine into citrulline, catalyzed by Ca(2+) dependent peptidylarginine deiminase enzyme (PAD), plays an essential role in physiological processes include gene expression regulation, apoptosis and the plasticity of the central nervous system, while aberrant citrullination can generate new epitopes, thus involving in the initiation and/or progression of autoimmune disorder like MS. Myelin basic protein (MBP) is the major myelin protein and is generally considered to maintain the stability of the myelin sheath. This review describes the MBP citrullination and its consequence, as well as offering further support for the "inside-out" hypothesis that MS is primarily a neurodegenerative disease with secondary inflammatory demyelination. In addition, it discusses the role of MBP citrullination in the immune inflammation and explores the potential of inhibition of PAD enzymes as a therapeutic strategy for the disease.

MMP-3 mediates psychosine-induced globoid cell formation: implications for leukodystrophy pathology

Globoid cell leukodystrophy (GLD) or Krabbe disease, is a fatal demyelinating disease attributed to mutations in the galactocerebrosidase (GALC) gene. Loss of function mutations in GALC result in accumulation of the glycolipid intermediate, galactosylsphingosine (psychosine). Due to the cytotoxicity of psychosine, it has been hypothesized that accumulated psychosine underlie the pathophysiology of GLD. However, the cellular mechanisms of GLD pathophysiology remain unclear. Globoid cells, multinucleated microglia/macrophages in the central nervous system (CNS), are a defining characteristic of GLD. Here we report that exposure of primary glial cultures to psychosine induces the expression and the production of matrix metalloproteinase (MMP)-3 that mediated a morphological transformation of microglia into a multinucleated globoid cell type. Additionally, psychosine-induced globoid cell formation from microglia was prevented by either genetic ablation or chemical inhibition of MMP-3. These effects are microglia-specific as peripheral macrophages exposed to psychosine did not become activated or express increased levels of MMP-3. In the brain from twitcher mice, a murine model of human GLD, elevated MMP-3 expression relative to wild-type littermates was contemporaneous with disease onset and further increased with disease progression. Further, bone marrow transplantation (BMT), currently the only therapeutically beneficial treatment for GLD, did not mitigate the elevated expression of MMP-3 in twitcher mice. Hence, elevated expression of MMP-3 in GLD may promote microglial responses to psychosine that may represent an important pathophysiological process in this disease and its treatment.

Matrix metalloproteinase-3 in the central nervous system: a look on the bright side

Matrix metalloproteinases (MMPs) are a large family of proteases involved in many cell-matrix and cell-cell signalling processes through activation, inactivation or release of extracellular matrix (ECM) and non-ECM molecules, such as growth factors and receptors. Uncontrolled MMP activities underlie the pathophysiology of many disorders. Also matrix metalloproteinase-3 (MMP-3) or stromelysin-1 contributes to several pathologies, such as cancer, asthma and rheumatoid arthritis, and has also been associated with neurodegenerative diseases like Alzheimer's disease, Parkinson's disease and multiple sclerosis. However, based on defined MMP spatiotemporal expression patterns, the identification of novel candidate molecular targets and in vitro and in vivo studies, a beneficial role for MMPs in CNS physiology and recovery is emerging. The main purpose of this review is to shed light on the recently identified roles of MMP-3 in normal brain development and in plasticity and regeneration after CNS injury and disease. As such, MMP-3 is correlated with neuronal migration and neurite outgrowth and guidance in the developing CNS and contributes to synaptic plasticity and learning in the adult CNS. Moreover, a strict spatiotemporal MMP-3 up-regulation in the injured or diseased CNS might support remyelination and neuroprotection, as well as genesis and migration of stem cells in the damaged brain.

Myelin loss associated with neuroinflammation in hypertensive rats

BACKGROUND AND PURPOSE

Small vessel disease is the major cause of white matter injury in patients with vascular cognitive impairment. Matrix metalloproteinase (MMP)-mediated inflammation may be involved in the white matter damage with oligodendrocyte (Ol) death. Therefore, we used spontaneously hypertensive stroke-prone rats to study the role of neuroinflammation in white matter damage.

METHODS

Permanent unilateral carotid artery occlusion was performed at 12 weeks of age in spontaneously hypertensive stroke-prone rats. Following surgery, rats were placed on a Japanese permissive diet and received 1% NaCl in drinking water. MRI, histology, biochemistry, and ELISA characterized white matter lesions, and cognitive impairment was tested by Morris water maze.

RESULTS

White matter damage was observed 4 to 5 weeks following permanent unilateral carotid artery occlusion/Japanese permissive diet. Immunoblotting showed marked reduction in myelin basic protein and upregulation of immature Ols. Mature Ols underwent caspase-3-mediated apoptosis. Morris water maze showed cognitive impairment. Abnormally appearing vessels were observed and surrounded by inflammatory-like cells. IgG extravasation and hemorrhage, indicating blood-brain barrier (BBB) disruption, was closely associated with MMP-9 expression. Lesions in white matter showed reactive astrocytosis and activated microglia that expressed tumor necrosis factor-α. MMP-3 and MMP-9 were significantly increased, and MMP-2 was reduced in both astrocytes and Ol.

CONCLUSIONS

We found apoptosis of mature Ols with an increase in immature Ols. Increased MMP-3, MMP-9, and tumor necrosis factor-α were associated with myelin breakdown and BBB disruption. Neuroinflammation is an important factor in white matter damage and Ol death, and studies using this new model can be performed to assess agents to block inflammation.

An alternate perspective on the roles of TIMPs and MMPs in pathology

Tissue inhibitors of metalloproteinases (TIMPs) are pleiotropic extracellular proteins. TIMPs are recognized as endogenous regulators of matrix metalloproteinases (MMPs), a large family of extracellular enzymes with proteolytic activities that participate in cellular homeostasis, adaptation, and tissue remodeling. In addition to their roles as endogenous potent MMP inhibitors, accumulating evidence indicates important physiological roles for TIMPs that are independent of their ability to block MMP activities. For instance, MMP-independent actions of TIMP-1 in the central nervous system have been implicated in synaptic plasticity, neuroprotection, oncogenesis, and oligodendrocyte differentiation. Expression of TIMP-1 is dramatically increased in response to a variety of injurious and inflammatory insults. In the context of disease pathogenesis, MMP and TIMP expression are interpreted with respect to the proteolytic consequences of increased MMP/TIMP ratios. Here, we provide an alternative perspective on the homeostatic balance of TIMP and MMP proteins, whereby consideration is given to the possible role of MMPs as cognate inhibitors of the signaling functions of TIMPs. Thus, MMPs may regulate the receptor-mediated actions of TIMPs, inasmuch as TIMPs are themselves inhibitors of MMP-mediated proteolytic activities. This broader view reflects our emerging understanding that TIMP signaling and MMP inhibition represent two important functions of TIMPs that have the potential to affect tissue pathology.

Matrix metalloproteinases and their tissue inhibitors in cuprizone-induced demyelination and remyelination of brain white and gray matter

Apart from their involvement in the pathogenesis of demyelinating diseases such as multiple sclerosis, there is emerging evidence that matrix metalloproteinases (MMPs) also promote remyelination. We investigated region-specific expression patterns of 11 MMPs and 4 tissueinhibitors of metalloproteinases (TIMPs) in the cuprizone murine demyelination model. Messenger RNA (mRNA) was extracted at different time points of exposure to cuprizone from microdissected samples of corpus callosum, cortex, and ex vivo isolated microglia and analyzedusing quantitative reverse transcription-polymerase chain reaction.Matrix metalloproteinase 12 and TIMP-1 mRNA were significantly upregulated versus age-matched controls in both areas during demyelination and remyelination. Matrix metalloproteinases 3, 11, and 14 mRNA were upregulated only in white matter during remyelination. Matrix metalloproteinase 24 mRNA was downregulated during both demyelination and remyelination. To identify potential cellular sources of the MMPs and TIMPs, we isolated microglia and detected high MMP-12and TIMP-2 mRNA upregulation at the peak of demyelination.By immunohistochemistry, MMP-3 protein was localized in astrocytes and MMP-12 was identified in microglia, astrocytes, and cells of oligodendrocyte lineage. These findings suggest that MMPs and TIMPs have roles in the regulation of demyelination and remyelination in thismodel. Moreover, differences in the expression levels of these genesbetween white and gray matter reveal region-specific molecularmechanisms.

[Functional degradation of myelin basic protein. Proteomic approach]

Proteolytic degradation of autoantigens is of prime importance in current biochemistry and immunology. The most fundamental issue in this field is the functional role of peptides produced when the specificity of hydrolysis changes during the shift from health to disease and from normal state to pathology. The identification of specific peptide fragments in many cases proposes the diagnostic and prognostic criterion in the pathology progression. The aim of this work is comparative study of the degradation peculiarities of one of the main neuroantigen, myelin basic protein by proteases, activated during progress of pathological demyelinating process, and by proteasome of different origin. The comparison of specificity of different studied biocatalysts gives reason to discuss the critical change in the set of myelin basic protein fragments capable to be presented by major histocompatibility complex class I during neurodegeneration, which can promote the progress of autoimmune pathological process.

Role of matrix metalloproteinase-3 in neurodegeneration

Matrix metalloproteinase-3 (MMP-3) is a member of the class of zinc-dependent proteases known to degrade the extracellular matrix. MMP-3 activity is regulated at three different levels: gene expression, proteolytic activation of the zymogen, and inhibition by the endogenous tissue inhibitors of metalloproteinase. A line of evidence indicates a role of MMP-3 in neurodegeneration. In neuronal cells, MMP-3 expression is increased in response to cell stress, and the cleaved, active MMP-3 participates in apoptotic signaling. In the extracellular space, MMP-3 triggers microglia to produce proinflammatory and cytotoxic molecules as well as MMP-3, which in turn contribute to neuronal damage. MMP-3 is increased in various experimental models of Parkinson's disease that are produced by selective toxins and by inflammagen, and the neuronal death is attenuated by various ways that inhibit MMP-3. α-Synuclein, whose gene mutations are associated with familial forms of Parkinson's disease, is proteolyzed by MMP-3. Contribution of MMP-3 toward the pathogenesis of Alzheimer's disease and other neurodegenerative diseases has also been suggested. Thus, modulation of MMP-3 expression and/or activity could be of therapeutic value for neurodegenerative diseases.

Melatonin protects against endometriosis via regulation of matrix metalloproteinase-3 and an apoptotic pathway

The role of matrix metalloproteinases (MMPs) in endometriosis, a gynecological disease of women, is unclear. The study investigated the activity of MMP-3 and its interplay with MMP-9 during the onset of endometriosis. Additionally, the importance of MMP-3 on the apoptotic pathway in endometriosis and effect of melatonin thereon were investigated. A Significant increase in the activity of MMP-3 with the severity of endometriosis in human was observed which was found similar in mice also. During the early phase of endometriosis, MMP-3 but not MMP-9 was increased and associated with the expression of transcription factor, c-Fos. Moreover, urokinase plasminogen activator and tissue inhibitor of metalloproteinase (TIMP)-3 were involved in MMP-3 regulation during endometriosis. Furthermore, MMP-3 activity that was parallel to c-Fos expression in endometriosis was reduced by melatonin pretreatment as characterized by diminished activator protein (AP)-1 DNA-binding activity. Because decreased apoptosis is an explanation for the perpetuation of endometriosis, we tested the role of melatonin on apoptotic pathway in preventing endometriosis. Significant regression of glandular epithelium was observed in melatonin-treated when compared to untreated mice. Melatonin treatment increased apoptotic cells in endometriotic zones. This was related to reduced Bcl-2 expression along with increased Bax expression and caspase-9 activation. In summary, early induction of MMP-3 was distinct from MMP-9 during endometriosis, which was regulated by c-Fos and TIMP-3. Melatonin suppressed MMP-3 activity and amplified apoptosis while regressing endometriosis through a caspase-3 mediated pathway. Thus, melatonin may be a therapeutic agent for resolving endometriosis.

TIMP-3 and MMP-3 contribute to delayed inflammation and hippocampal neuronal death following global ischemia

Hippocampal neuronal death following transient global ischemia in the mouse takes days to occur, providing a potential timeframe for therapeutic intervention. Since matrix metalloproteinase-3 (MMP-3) enhances inflammation and tissue inhibitor of metalloproteinases-3 (TIMP-3) promotes apoptosis in ischemia, we hypothesized that they are involved in neuronal death secondary to transient global ischemia. Timp-3 knockout (T3KO) and wild type (T3WT) mice underwent 30 min bilateral carotid artery occlusion (BCAO), which causes hippocampal neuronal death 7 days after reperfusion. Mice lacking the Timp-3 gene have significantly less astrocytosis, microglial reactivity, MMP-3 activity and neuronal cell death. In addition, T3KO mice had decreased tumor necrosis factor (TNF) receptor-1 (TNFR1) expression and increased TNF-alpha converting enzyme (TACE) activity. Mmp-3 KO mice with a similar BCAO showed significantly fewer microglial cells, reduced TNF-alpha expression, and less neuronal death than the Mmp-3 WT. To see if TIMP-3 and MMP-3 cell death pathways were independent, we blocked MMPs with the broad-spectrum MMP inhibitor, BB-94, on days 3 through 6 of reperfusion in T3WT and T3KO mice. BB-94 rescued hippocampal neurons at 7 days in both T3WT and T3KO mice, but significantly fewer neurons died in T3KO mice treated with BB-94. Our results indicate a novel additive role for TIMP-3 and MMP-3 in delayed neuronal death, and show that delayed treatment with MMP inhibitors can be used to reduce hippocampal death.

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.

Matrix metalloproteinase-3 expression profile differentiates adaptive and maladaptive synaptic plasticity induced by traumatic brain injury

The interaction between extracellular matrix (ECM) and regulatory matrix metalloproteinases (MMPs) is important in establishing and maintaining synaptic connectivity. By using fluid percussion traumatic brain injury (TBI) and combined TBI and bilateral entorhinal cortical lesion (TBI + BEC), we previously demonstrated that hippocampal stromelysin-1 (MMP-3) expression and activity increased during synaptic plasticity. We now report a temporal analysis of MMP-3 protein and mRNA response to TBI during both degenerative (2 day) and regenerative (7, 15 day) phases of reactive synaptogenesis. MMP-3 expression during successful synaptic reorganization (following unilateral entorhinal cortical lesion; UEC) was compared with MMP-3 expression when normal synaptogenesis fails (after combined TBI + BEC insult). Increased expression of MMP-3 protein and message was observed in both models at 2 days postinjury, and immuohistochemical (IHC) colocalization suggested that reactive astrocytes contribute to that increase. By 7 days postinjury, model differences in MMP-3 were observed. UEC MMP-3 mRNA was equivalent to control, and MMP-3 protein was reduced within the deafferented region. In contrast, enzyme mRNA remained elevated in the maladaptive TBI + BEC model, accompanied by persistent cellular labeling of MMP-3 protein. At 15 days survival, MMP-3 mRNA was normalized in each model, but enzyme protein remained higher than paired controls. When TBI + BEC recovery was enhanced by the N-methyl-D-aspartate antagonist MK-801, 7-day MMP-3 mRNA was significantly reduced. Similarly, MMP inhibition with FN-439 reduced the persistent spatial learning deficits associated with TBI + BEC insult. These results suggest that MMP-3 might differentially affect the sequential phases of reactive synaptogenesis and exhibit an altered pattern when recovery is perturbed.

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.

Cell and agonist-specific regulation of genes for matrix metalloproteinases and their tissue inhibitors by primary glial cells

An imbalance in the matrix metalloproteinase (MMP) : tissue inhibitor of MMP (TIMP) ratio may be associated with tissue injury. Here, we studied the regulation of TIMP and MMP gene expression in primary glial cultures to ascertain the factors involved in the regulation of these genes in conditions of inflammatory neuropathology. Astrocytes were found to basally express TIMP-1 and TIMP-3 mRNA while microglia expressed only TIMP-2 mRNA. TIMP-4 mRNA was not detectable in either cell type. Treatment with interferon-alpha (IFN-alpha), IFN-gamma, interleukin-3 (IL-3), IL-6 or tumor necrosis factor-alpha (TNF-alpha) did not alter expression of the TIMP genes. However, in astrocytes, but not in microglia, serum, IL-1beta or lipopolysaccharide (LPS) evoked a dose- and time-dependent increase in TIMP-1 mRNA and a coincident down-regulation of the TIMP-3 gene. Astrocytes were found to express mRNA constitutively for MMPs -3, -11 and -14. In contrast, microglia expressed only MMP-12 mRNA under basal conditions. IL-1beta enhanced MMP-3 mRNA levels while LPS increased the MMP-3, -9, -12, -13 and -14 mRNAs. Our findings reveal that regulatory control of TIMP and MMP gene expression by glial cells is agonist- and cell-type specific, and suggest that innate immune signals govern the temporal and spatial expression patterns of TIMP and MMP genes in neuroinflammatory conditions of the CNS.

Differences in susceptibility of MBP charge isomers to digestion by stromelysin-1 (MMP-3) and release of an immunodominant epitope

Charge microheterogeneity of myelin basic protein is known to affect its conformation and function. Here, the citrullinated myelin basic protein charge isomer, component-8, was shown to be more susceptible to stromelysin-1 cleavage than myelin basic protein component-1. Since levels of component-8 are increased in multiple sclerosis brain, the increased susceptibility of component-8 to proteolytic digestion may play a role in the pathogenesis of multiple sclerosis. Interestingly, component-1 isolated from multiple sclerosis patients was digested at a faster rate by stromelysin-1 than component-1 isolated from normal individuals. The reason for this difference is not clear, but likely reflects conformational differences between the two proteins as a result of post-translational modifications. Stromelysin-1 was able to cleave myelin basic protein in the presence of lipids and within the context of myelin and released several peptides including peptides containing the immunodominant epitope.

Serum matrix metalloproteinase-3 levels correlate with disease activity in relapsing-remitting multiple sclerosis

BACKGROUND

Adhesion molecules and matrix metalloproteinases (MMPs) are known to be relevant to the ongoing development and disappearance of areas of demyelination in the white matter of the CNS of multiple sclerosis (MS) patients. This study examined whether serum matrix metalloproteinase-3 (MMP-3) levels correlate with disease activity in MS.

METHODS

Serum MMP-3 levels in 47 consecutive patients with relapsing-remitting MS were measured by immunoassay every 4 weeks over a 15 month period.

RESULTS

During the study period, 48 clinical relapses occurred. Serum MMP-3 levels within 1 month of relapse were significantly higher than during the remission phase. Sequential analysis showed that serum MMP-3 levels had increased transiently at the time of clinical relapse but returned to the normal range within a month.

CONCLUSIONS

Circulatory MMP-3 levels are correlated with disease activity in relapsing-remitting MS. This may contribute to the breakdown of the blood-brain barrier at the time of relapse.

Isolation, characterization, and expression of stromelysin-1 in primary tumors of dogs

OBJECTIVE

To isolate and characterize the cDNA sequence of canine stromelysin-1 (matrix metalloproteinase [MMPI-3), screen various naturally developing primary tumors of dogs, and assess the effect of stromelysin-1 on survival of dogs with cancer.

SAMPLE POPULATION

3 canine cell lines and biopsy specimens of primary tumors collected from 54 dogs.

PROCEDURE

3 canine cell lines and biopsy specimens of primary tumors collected from 54 dogs at the University of Illinois Veterinary Teaching Hospital were used in the study. Primer sets based on human stromelysin-1 and consensus sequences were designed for expression, screening, and isolation. Two additional primer sets were designed for screening. Samples were assayed at least in duplicate. Data were analyzed for differences in expression of stromelysin-1 on the basis of sex, age, metastasis, malignant versus nonmalignant tissue origin, and duration of patient survival.

RESULTS

A 1,479-bp cDNA nucleotide sequence was amplified from established canine cell lines. The open reading frame encoded a protein consisting of 478 amino acids. This sequence was 70% to 88% homologous with stromelysin-1 of other species at the amino acid level. Fifty-four samples were screened for stromelysin-1. Of these, 34 (63%) had positive results and 20 (37%) had negative results for expression. Stromelysin-1 and metastasis were associated with a poor prognosis for survival.

CONCLUSIONS AND CLINICAL RELEVANCE

Stromelysin-1 is a potential activator of other members of the MMP family. Additional studies are needed to investigate the relationship between stromelysin-1 production and aggressive biological behavior of tumors in dogs.

Elevation of hippocampal MMP-3 expression and activity during trauma-induced synaptogenesis

The matrix metalloproteinase (MMP) enzyme family contributes to the regulation of a variety of brain extracellular matrix molecules. In order to assess their role in synaptic plasticity following traumatic brain injury (TBI), we compared expression of stromelysin-1 (MMP-3) protein and mRNA in two rodent models of TBI exhibiting different levels of recovery: adaptive synaptic plasticity following central fluid percussion injury and maladaptive synaptic plasticity generated by combined TBI and bilateral entorhinal cortical lesion (TBI + BEC). We sampled the hippocampus at 7 days postinjury, targeting a selectively vulnerable brain region and a survival interval exhibiting rapid synaptogenesis. We report elevated expression of hippocampal MMP-3 mRNA and protein after TBI. MMP-3 immunohistochemical staining showed increased protein levels relative to sham-injured controls, primarily localized to cell bodies within the deafferented dendritic laminae. Injury-related differences in MMP-3 protein were also observed. TBI alone elevated MMP-3 immunobinding over the stratum lacunosum moleculare (SLM), inner molecular layer and hilus, while TBI + BEC generated more robust increases in MMP-3 reactivity within the deafferented SLM and dentate molecular layer (DML). Double labeling with GFAP confirmed the presence of MMP-3 within reactive astrocytes induced by each injury model. Semi-quantitative RT-PCR revealed that MMP-3 mRNA also increased after each injury, however, the combined insult induced a much greater elevation than fluid percussion alone: 1.9-fold vs. 79%, respectively. In the TBI + BEC model, MMP-3 up-regulation was spatio-temporally correlated with increased enzyme activity, an effect which was attenuated with the neuroprotective compound MK-801. These results show that distinct pathological conditions elicited by TBI can differentially affect MMP-3 expression during reactive synaptic plasticity. Notably, these effects are both transcriptional and translational and are correlated with functionally active enzyme.

Expression of matrix metalloproteinases in feline vaccine site-associated sarcomas

OBJECTIVES

To screen for expression of 9 predominant members of the matrix metalloproteinase (MMP) family, including membrane-type matrix metalloproteinases (MT-MMPs) and tissue inhibitors of metalloproteinases (TIMPs), in primary tumor tissue biopsy specimens of vaccine site-associated sarcomas (VSS) in cats and compare expression profiles of VSS with expression profiles of non-VSS and carcinomas.

SAMPLE POPULATION

31 primary tumor tissue biopsy specimens and 6 nontumor (normal) tissue biopsy specimens.

PROCEDURES

Tissue specimens were obtained from primary tumor biopsy specimens of cats. Primers for reverse transcriptase-polymerase chain reaction assay were designed on the basis of known sequences. Data were analyzed for patterns of expression of MMPs, MT-MMPs, and TIMPs. Differences in expression patterns were evaluated among cats of differing genders, ages, metastasis status, and overall survival durations, and between cats with VSS and cats with non-VSS tumor types.

RESULTS

A total of 31 primary tumor tissue biopsy specimens and 6 nontumor (normal) tissue biopsy specimens were screened for the presence of 6 MMPs and 3 TIMPs. Matrix metalloproteinase and TIMP expression was found in non-VSS, carcinomas, and VSS. No significant differences were found in patterns of expression among tumor types. Metastasis was found to be the only predictive factor for overall survival duration. A significant correlation was found between MMP2 and MT-MMP16 expression and overall duration of survival.

CONCLUSIONS AND CLINICAL RELEVANCE

The identification of MMPs in feline VSS supports an underlying inflammatory pathogenesis for this tumor. Expression of MMP2 and MT-MMP16 were correlated with survival time in our study.

Activation of Matrix Metalloproteinase-3 and Agrin Cleavage in Cerebral Ischemia/Reperfusion

Matrix metalloproteinase-3 (MMP-3) degrades components of the extracellular matrix and may participate in the pathogenesis of stroke. Here we examine the expression, activation, and cellular location of MMP-3 and the cleavage of agrin, an MMP-3 substrate, following transient middle cerebral artery occlusion in the rat. MMP-3 was activated by ischemia/reperfusion, which was revealed by the appearance of a cleaved form and increased degradation of a substrate. MMP-3 was observed in ischemic neurons, oligodendrocytes, microvasculature, and reactive microglia/macrophages. In cell cultures, MMP-3 expression was observed in neurons and, to a lesser extent, in mature oligodendrocytes, but not in oligodendrocyte progenitors, astrocytes, or microglia. Casein zymography revealed MMP-3 in cultured neurons. Agrin was expressed in cultured neurons and cultured astrocytes. In brain tissue, agrin was detected in neurons, and following ischemia it was also detected in reactive astrocytes. Addition of MMP-3 to protein extracts from control brain caused neuronal agrin degradation. Following ischemia/reperfusion, agrin disappeared from the tissue membrane fraction and a cleaved agrin fragment was found in tissue protein extracts. The present results show MMP-3 activation and neuronal transmembrane agrin cleavage after ischemia/reperfusion. In addition, the finding that MMP-3 cleaves brain agrin strongly suggests that ischemia-induced MMP-3 activation causes agrin cleavage.

Isolation, characterization, and expression of feline stromelysin-1 in naturally developing tumors in cats

OBJECTIVE

To detect, isolate, and characterize feline stromelysin-1 (ie, matrix metalloproteinase [MMP]-3) in naturally developing tumors in cats.

SAMPLE POPULATION

31 tissue samples obtained from primary tumors and 6 samples of normal tissues from cats.

PROCEDURE

Biopsy specimens were obtained from primary tumors. Primers were designed on the basis of known sequences. The sequence of stromelysin-1 was cloned and analyzed. An additional primer set was used as a screening tool. Samples were assayed in duplicate or triplicate, when possible. Data obtained were analyzed for differences in expression of stromelysin-1 with regard to overall survival among cats of various sex, age, and disease status.

RESULTS

A 1,181-bp cDNA nucleotide sequence was amplified. The open reading frame encoded 393 amino acids. This amino acid sequence shared 70% to 85% sequence homology with sequences of other species. In addition, samples were screened for stromelysin-1. Of the 31 tumor samples tested, 16 (51.6%) had positive results for expression of stromelysin-1. Total RNA expression was detected in a diverse group of tumor types. Prognostic factors associated with a shorter duration of survival included evidence of metastasis and metastasis associated with expression of stromelysin-1.

CONCLUSIONS AND CLINICAL RELEVANCE

Feline stromelysin-1 contains all the conserved regions typically found in members of the MMP family. Activity of stromelysin-1 has been implicated in a wide number of physiologic and pathologic processes. Identification of this gene may lead to the development of useful reagents to assist with diagnosis and management of neoplastic diseases in cats.

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.

Functional roles and therapeutic targeting of gelatinase B and chemokines in multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the CNS of unknown cause. Pathogenetic mechanisms, such as chemotaxis, subsequent activation of autoreactive lymphocytes, and skewing of the extracellular proteinase balance, are targets for new therapies. Matrix metalloproteinase gelatinase B (MMP-9) is upregulated in MS and was recently shown to degrade interferon beta, one of the drugs used to treat MS. Consequently, the effect of endogenously produced interferon beta or parenterally given interferon beta may be increased by gelatinase B inhibitors. Blockage of chemotaxis or cell adhesion molecule engagement, and inhibition of hydroxymethyl-glutaryl-coenzyme-A reductase to lower expression of gelatinase B, may become effective treatments of MS, alone or in combination with interferon beta. This may allow interferon beta to be used at lower doses and prevent side-effects.