Multiple sclerosis: elevated expression of matrix metalloproteinases in blood monocytes

Differences in Acute Expression of Matrix Metalloproteinases-9, 3, and 2 Related to the Duration of Brain Ischemia and Tissue Plasminogen Activator Treatment in Experimental Stroke

Matrix metalloproteinases (MMPs) such as MMP-9, 3, and 2 degrade the cellular matrix and are believed to play a crucial role in ischemic stroke. We examined how the duration of ischemia (up to 4 h) and treatment with recombinant tissue plasminogen activator altered the comparative expression of these MMPs in experimental ischemic stroke with reperfusion. Both prolonged ischemia and r-tPA treatment markedly increased MMP-9 expression in the ischemic hemisphere (all p < 0.0001). The duration of ischemia and r-tPA treatment also significantly increased MMP-2 expression (p < 0.01-0.001) in the ischemic hemisphere (p < 0.01) but to a lesser degree than MMP-9. In contrast, MMP-3 expression significantly decreased in the ischemic hemisphere (p < 0.001) with increasing duration of ischemia and r-tPA treatment (p < 0.05-0001). MMP-9 expression was prominent in the vascular compartment and leukocytes. MMP-2 expression was evident in the vascular compartment and MMP-3 in NeuN+ neurons. Prolonging the duration of ischemia (up to 4 h) before reperfusion increased brain hemorrhage, infarction, swelling, and neurologic disability in both saline-treated (control) and r-tPA-treated mice. MMP-9 and MMP-2 expression were significantly positively correlated with, and MMP-3 was significantly negatively correlated with, infarct volume, swelling, and brain hemorrhage. We conclude that in experimental ischemic stroke with reperfusion, the duration of ischemia and r-tPA treatment significantly altered MMP-9, 3, and 2 expression, ischemic brain injury, and neurological disability. Each MMP showed unique patterns of expression that are strongly correlated with the severity of brain infarction, swelling, and hemorrhage. In summary, in experimental ischemic stroke in male mice with reperfusion, the duration of ischemia, and r-tPA treatment significantly altered the immunofluorescent expression of MMP-9, 3, and 2, ischemic brain injury, and neurological disability. In this model, each MMP showed unique patterns of expression that were strongly correlated with the severity of brain infarction, swelling, and hemorrhage.

Atorvastatin attenuates NS1 (Non-structural protein-1) of dengue type-2 serotype-induced expressions of matrix metalloproteinases in HL-60 cells, differentiated to neutrophils: Implications for the immunopathogenesis of dengue viral disease

BACKGROUND

The dengue is a vector borne viral infection in humans. Bite of mosquito infected with a dengue virus transmits the disease. The neutrophils support more to the innate immune response by switching to infected tissues and triggering immunomodulatory mechanisms including the release of proteases and host defence peptides.

METHODS

Cell viability by MTT and trypan blue dye exclusion assay, bright field microscopy for assessment of cell morphology, cytokines measurements by ELISA, estimation of protein by Bradford assay were done. Assessments of matrix metalloproteinase genes mRNA expressions were done using real-time PCR.

RESULTS

In the present study, we have for the first time unveiled that, NS1 antigen of dengue type-2 serotype, induce and stimulate the neutrophils cells to express high levels of matrix metalloproteases. NS1 exposure of HL-60 cells differentiated to neutrophils affected cell morphology and in 24 h of exposure. We have demonstrated that, the NS1 antigen has induced MMP-2, MMP-14 and MMP-9 expressions in neutrophils in a 24hrs exposure time. NS1 exposure has also further upregulated MMP-1, MMP-13, and MMP-8 expressions in neutrophils in a 24hrs exposure time. Notably, treatment with atorvastatin concentrations downregulated the expression profile of the all matrix metalloprotease significantly. Importantly, NS1 antigen has significantly increased the IL-6, IL-13 release by the HL,60 cells which was reversed by atorvastatin. On the other hand, NS1 exposure enhanced the mRNA expressions of VEGF-A and VEGF-D which was reversed by atorvastatin. However, we found that, NS1 exposure reduced the mRNA expressions profile of VEGF-C, which was reversed by atorvastatin.

CONCLUSION

In conclusion, we report that, neutrophils associated matrix metalloprotease are involved in the pathogenesis of dengue viral disease. VEGF growth factors may also be released by the neutrophils which may subsequently participate in the endothelial dysfunctions leading to dengue shock syndrome.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood-brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

The Impact of Obesity on Microglial Function: Immune, Metabolic and Endocrine Perspectives

Increased life expectancy in combination with modern life style and high prevalence of obesity are important risk factors for development of neurodegenerative diseases. Neuroinflammation is a feature of neurodegenerative diseases, and microglia, the innate immune cells of the brain, are central players in it. The present review discusses the effects of obesity, chronic peripheral inflammation and obesity-associated metabolic and endocrine perturbations, including insulin resistance, dyslipidemia and increased glucocorticoid levels, on microglial function.

Multimodal peripheral fluid biomarker analysis in clinically isolated syndrome and early multiple sclerosis

BACKGROUND

Increasing evidence suggests that various inflammatory, immunological and metabolic pathways are altered in the clinically isolated syndrome (CIS) of multiple sclerosis (MS). Moreover, recent diagnostic criteria have made possible the very early diagnosis of MS. We evaluated multiple fluid biomarkers in people with early MS and CIS.

METHODS

We measured blood levels of cytokines, matrix metalloproteinases (MMPs), serum metabolomics and immune cell immunophenotyping in participants in the Trial of Minocycline in a Clinically Isolated Syndrome of Multiple Sclerosis.

RESULTS

When compared with healthy controls, people with early MS/CIS had higher levels of eotaxin, MCP-3, IL-1 receptor antagonist, IL-1β, IL-9 and IP-10, as well as MMPs 1, 8 and 9. In metabolomics analysis, the alanine, aspartate and glutamate metabolism and the synthesis and degradation of ketone bodies pathways were altered compared to healthy controls. There were no differences in lymphocyte subpopulation numbers. Out of all these biomarkers, only MMP-1 was able to differentiate between early MS and CIS, and was found to correlate with lesion volume and gadolinium enhancing lesions on MRI.

CONCLUSION

The immunological and metabolic profile of CIS and early MS is remarkably similar, supporting that these are a continuum of a common underlying pathophysiological process.

Multifaceted Role of Matrix Metalloproteinases in Neurodegenerative Diseases: Pathophysiological and Therapeutic Perspectives

Neurodegeneration is the pathological condition, in which the nervous system or neuron loses its structure, function, or both, leading to progressive degeneration or the death of neurons, and well-defined associations of tissue system, resulting in clinical manifestations. Neuroinflammation has been shown to precede neurodegeneration in several neurodegenerative diseases (NDs). No drug is yet known to delay or treat neurodegeneration. Although the etiology and potential causes of NDs remain widely indefinable, matrix metalloproteinases (MMPs) evidently have a crucial role in the progression of NDs. MMPs, a protein family of zinc (Zn²⁺)-containing endopeptidases, are pivotal agents that are involved in various biological and pathological processes in the central nervous system (CNS). The current review delineates the several emerging evidence demonstrating the effects of MMPs in the progression of NDs, wherein they regulate several processes, such as (neuro)inflammation, microglial activation, amyloid peptide degradation, blood brain barrier (BBB) disruption, dopaminergic apoptosis, and α-synuclein modulation, leading to neurotoxicity and neuron death. Published papers to date were searched via PubMed, MEDLINE, etc., while using selective keywords highlighted in our manuscript. We also aim to shed a light on pathophysiological effect of MMPs in the CNS and focus our attention on its detrimental and beneficial effects in NDs, with a special focus on Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), multiple sclerosis (MS), and Huntington's disease (HD), and discussed various therapeutic strategies targeting MMPs, which could serve as potential modulators in NDs. Over time, several agents have been developed in order to overcome challenges and open up the possibilities for making selective modulators of MMPs to decipher the multifaceted functions of MMPs in NDs. There is still a greater need to explore them in clinics.

TIMP-1 Attenuates the Development of Inflammatory Pain Through MMP-Dependent and Receptor-Mediated Cell Signaling Mechanisms

Unresolved inflammation is a significant predictor for developing chronic pain, and targeting the mechanisms underlying inflammation offers opportunities for therapeutic intervention. During inflammation, matrix metalloproteinase (MMP) activity contributes to tissue remodeling and inflammatory signaling, and is regulated by tissue inhibitors of metalloproteinases (TIMPs). TIMP-1 and -2 have known roles in pain, but only in the context of MMP inhibition. However, TIMP-1 also has receptor-mediated cell signaling functions that are not well understood. Here, we examined how TIMP-1-dependent cell signaling impacts inflammatory hypersensitivity and ongoing pain. We found that hindpaw injection of complete Freund’s adjuvant (CFA) increased cutaneous TIMP-1 expression that peaked prior to development of mechanical hypersensitivity, suggesting that TIMP-1 inhibits the development of inflammatory hypersensitivity. To examine this possibility, we injected TIMP-1 knockout (T1KO) mice with CFA and found that T1KO mice exhibited rapid onset thermal and mechanical hypersensitivity at the site of inflammation that was absent or attenuated in WT controls. We also found that T1KO mice exhibited hypersensitivity in adjacent tissues innervated by different sets of afferents, as well as skin contralateral to the site of inflammation. Replacement of recombinant murine (rm)TIMP-1 alleviated hypersensitivity when administered at the site and time of inflammation. Administration of either the MMP inhibiting N-terminal or the cell signaling C-terminal domains recapitulated the antinociceptive effect of full-length rmTIMP-1, suggesting that rmTIMP-1inhibits hypersensitivity through MMP inhibition and receptor-mediated cell signaling. We also found that hypersensitivity was not due to genotype-specific differences in MMP-9 activity or expression, nor to differences in cytokine expression. Administration of rmTIMP-1 prevented mechanical hypersensitivity and ongoing pain in WT mice, collectively suggesting a novel role for TIMP-1 in the attenuation of inflammatory pain.

MMPs and ADAMs in neurological infectious diseases and multiple sclerosis

Metalloproteinases-such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs)-are involved in various diseases of the nervous system but also contribute to nervous system development, synaptic plasticity and neuroregeneration upon injury. MMPs and ADAMs proteolytically cleave many substrates including extracellular matrix components but also signaling molecules and receptors. During neuroinfectious disease with associated neuroinflammation, MMPs and ADAMs regulate blood-brain barrier breakdown, bacterial invasion, neutrophil infiltration and cytokine signaling. Specific and broad-spectrum inhibitors for MMPs and ADAMs have experimentally been shown to decrease neuroinflammation and brain damage in diseases with excessive neuroinflammation as a common denominator, such as pneumococcal meningitis and multiple sclerosis, thereby improving the disease outcome. Timing of metalloproteinase inhibition appears to be critical to effectively target the cascade of pathophysiological processes leading to brain damage without inhibiting the neuroregenerative effects of metalloproteinases. As the critical role of metalloproteinases in neuronal repair mechanisms and regeneration was only lately recognized, the original idea of chronic MMP inhibition needs to be conceptually revised. Recently accumulated research urges for a second chance of metalloproteinase inhibitors, which-when correctly applied and dosed-harbor the potential to improve the outcome of different neuroinflammatory diseases.

Matrix metalloproteinases in the CNS: interferons get nervous

Matrix metalloproteinases (MMPs) have been investigated in context of chronic inflammatory diseases and demonstrated to degrade multiple components of the extracellular matrix (ECM). However, following several disappointing MMP clinical trials, recent studies have demonstrated unexpected novel functions of MMPs in viral infections and autoimmune inflammatory diseases in unanticipated locations. Thus, MMPs play additional functions in inflammation than just ECM degradation. They can regulate the activity of chemokines and cytokines of the immune response by precise proteolytic processing resulting in activation or inactivation of signaling pathways. MMPs have been demonstrated to cleave multiple substrates of the central nervous systems (CNS) and contribute to promoting and dampening diseases of the CNS. Initially, believed to be solely promoting pathologies, more than 10 MMPs to date have been shown to have protective functions. Here, we present some of the beneficial and destructive roles of MMPs in CNS pathologies and discuss strategies for the use of MMP inhibitors.

Increased expression of mir-301a in PBMCs of patients with relapsing-remitting multiple sclerosis is associated with reduced NKRF and PIAS3 expression levels and disease activity

Most of the multiple sclerosis (MS) patients are initially diagnosed with relapsing remitting multiple sclerosis (RRMS). Th17 cells and macrophages have been shown to play critical roles in pathogenesis of MS and initiation of CNS tissue damage. MiR-301a have recently been exposed as an activator of STAT3 in Th17 cells as well as an activator of NF-κB in macrophages by targeting PIAS3 and NKRF correspondingly. However, the possible role of miR-301a in RRMS has not yet been elucidated. Herewith, for the first time, we have studied the expression of miR-301a, NKRF and PIAS3 by quantitative real-time PCR and western blotting method in peripheral blood mononuclear cells (PBMCs) of 71 RRMS patients, including two groups of patients in relapse phase (n = 44) and a group of remitting phase patients (n = 28) in comparison to healthy volunteers (n = 28). In this work, we demonstrate a significant upregulation of miR-301a in relapse phase of MS patients compared to healthy controls and remitting phase patients (P < .05). Our findings also showed a striking decrease of NKRF and PIAS3 expression in relapse phase patients, in contrast to miR-301a and, NF-κB and STAT3 downstream genes (SKA2 and RORc) (P < .05). Subsequently, using luciferase reporter system we confirmed that miR-301a directly targets the mRNA encoding PIAS3 and NKRF proteins. We also showed that miR-301a increasing expression is correlated with down-regulation of PIAS3 and NKRF expression in RRMS patients. Our findings suggest that miR-301a, PIAS3 and NKRF play crucial roles in RRMS and could be considered as promising therapeutic targets.

Multiple sclerosis and air pollution exposure: Mechanisms toward brain autoimmunity

The association between neurodegenerative diseases and environmental exposures, in particular air pollution, has been noticed in the last two decades, but the importance of this environmental factor in multiple sclerosis (MS) pathogenesis has not been considered extensively. However, recent evidence suggests that major mechanisms involved in MS pathogenesis, such as inflammatory factors expression, free radicals overproduction, the blood brain barrier (BBB) breakdown, neuroinflammation, vitamin D deficiency and mitochondrial dysfunction could also occur due to exposure to air pollutants. A prospective hypothesis is suggested here in which exposure to air pollutants may initiate destructive mechanisms inducing inflammatory-oxidative cascades, reduction of immunological self-tolerance and neurodegeneration leading to brain autoimmunity.

Matrix metalloproteinases in the brain and blood-brain barrier: Versatile breakers and makers

Matrix metalloproteinases are versatile endopeptidases with many different functions in the body in health and disease. In the brain, matrix metalloproteinases are critical for tissue formation, neuronal network remodeling, and blood-brain barrier integrity. Many reviews have been published on matrix metalloproteinases before, most of which focus on the two best studied matrix metalloproteinases, the gelatinases MMP-2 and MMP-9, and their role in one or two diseases. In this review, we provide a broad overview of the role various matrix metalloproteinases play in brain disorders. We summarize and review current knowledge and understanding of matrix metalloproteinases in the brain and at the blood-brain barrier in neuroinflammation, multiple sclerosis, cerebral aneurysms, stroke, epilepsy, Alzheimer's disease, Parkinson's disease, and brain cancer. We discuss the detrimental effects matrix metalloproteinases can have in these conditions, contributing to blood-brain barrier leakage, neuroinflammation, neurotoxicity, demyelination, tumor angiogenesis, and cancer metastasis. We also discuss the beneficial role matrix metalloproteinases can play in neuroprotection and anti-inflammation. Finally, we address matrix metalloproteinases as potential therapeutic targets. Together, in this comprehensive review, we summarize current understanding and knowledge of matrix metalloproteinases in the brain and at the blood-brain barrier in brain disorders.

Friends or Foes: Matrix Metalloproteinases and Their Multifaceted Roles in Neurodegenerative Diseases

Neurodegeneration is a chronic progressive loss of neuronal cells leading to deterioration of central nervous system (CNS) functionality. It has been shown that neuroinflammation precedes neurodegeneration in various neurodegenerative diseases. Matrix metalloproteinases (MMPs), a protein family of zinc-containing endopeptidases, are essential in (neuro)inflammation and might be involved in neurodegeneration. Although MMPs are indispensable for physiological development and functioning of the organism, they are often referred to as double-edged swords due to their ability to also inflict substantial damage in various pathological conditions. MMP activity is strictly controlled, and its dysregulation leads to a variety of pathologies. Investigation of their potential use as therapeutic targets requires a better understanding of their contributions to the development of neurodegenerative diseases. Here, we review MMPs and their roles in neurodegenerative diseases: Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and multiple sclerosis (MS). We also discuss MMP inhibition as a possible therapeutic strategy to treat neurodegenerative diseases.

EMMPRIN, an upstream regulator of MMPs, in CNS biology

Matrix metalloproteinases (MMPs) are engaged in pathologies associated with infections, tumors, autoimmune disorders and neurological dysfunctions. With the identification of an upstream regulator of MMPs, EMMPRIN (Extracellular matrix metalloproteinase inducer, CD147), it is relevant to address if EMMPRIN plays a role in the pathology of central nervous system (CNS) diseases. This would enable the possibility of a more upstream and effective therapeutic target. Indeed, conditions including gliomas, Alzheimer's disease (AD), multiple sclerosis (MS), and other insults such as hypoxia/ischemia show elevated levels of EMMPRIN which correlate with MMP production. In contrast, given EMMPRIN's role in CNS homeostasis with respect to regulation of monocarboxylate transporters (MCTs) and interactions with adhesion molecules including integrins, we need to consider that EMMPRIN may also serve important regulatory or protective functions. This review summarizes the current understanding of EMMPRIN's involvement in CNS homeostasis, its possible roles in escalating or reducing neural injury, and the mechanisms of EMMPRIN including and apart from MMP induction.

MS susceptibility is not affected by single nucleotide polymorphisms in the MMP9 gene

Matrix metalloproteinase 9 (MMP9) plays an important role in the pathogenesis of multiple sclerosis (MS). However, the impact of genetic variants affecting MMP9 on MS susceptibility is still in debate. We could not detect an association of MMP9 SNPs with MS on a genome-wide significance level by SNP genotyping, followed by imputation of SNPs within a region stretching 2Mbp up- and down-stream of MMP9. Rs6073751, located within WFDC2, was found associated with MS most strongly. Rs3918242, associated with MS according to previous reports, showed nominal significance only. Meta-analysis of our own and published data did not confirm this effect.

Overexpression of MMP-9 and its inhibitors in blood mononuclear cells after myocardial infarction--is it associated with depressive symptomatology?

Background

Matrix metalloproteinase (MMP)-9 may play a central role in the development and progression of atherosclerosis. Emerging evidence also indicates an association between MMP-9 and depressive symptomatology. Here, we investigated whether expression of MMP-9 and its inhibitors in blood mononuclear cells and plasma were related to depressive symptoms in patients with a recent myocardial infarction (MI).

Methods and Results

Blood sampling was performed between 6 and 18 months after MI in 57 patients. Forty-one clinically healthy subjects were included as controls. Gene expression of MMP-9 and its main tissue inhibitors TIMP-1 and -2 were analyzed in freshly isolated or cultured blood mononuclear cells. Corresponding protein levels were assessed in cell supernatants and plasma. In post-MI patients, mRNA levels of MMP-9 and TIMP-1 and -2 were significantly higher than in controls while protein levels in cell supernatants and plasma did not differ between groups. The Center for Epidemiological Studies - Depression (CES-D) scale was used to assess depressive symptomatology. Repeated assessments during the first 18 months after MI showed significantly higher CES-D scores in patients compared with controls. However, there were no relationships between depressive mood and any of the measurements of MMP-9 or TIMPs.

Conclusion

Our findings indicate that overexpression of MMP-9 and TIMPs in blood mononuclear cells and elevated depressive symptoms represent two unrelated phenomena after MI.

The significance of matrix metalloproteinases in the immunopathogenesis and treatment of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS). The major pathological outcomes of the disease are the loss of blood-brain barrier (BBB) integrity and the development of reactive astrogliosis and MS plaque. For the disease to occur, the non-resident cells must enter into the immune-privileged CNS through a breach in the relatively impermeable BBB. It has been demonstrated that matrix metalloproteinases (MMPs) play an important role in the immunopathogenesis of MS, in part through the disruption of the BBB and the recruitment of inflammatory cells into the CNS. Moreover, MMPs can also enhance the cleavage of myelin basic protein (MBP) and the demyelination process. Regarding the growing data on the roles of MMPs and their tissue inhibitors (TIMPs) in the pathogenesis of MS, this review discusses the role of different types of MMPs, including MMP-2, -3, -7, -9, -12 and -25, in the immunopathogenesis and treatment of MS.

Zymographic patterns of MMP-2 and MMP-9 in the CSF and cerebellum of dogs with subacute distemper leukoencephalitis

Distemper leukoencephalitis is a disease caused by the canine distemper virus (CDV) infection. It is a demyelinating disease affecting mainly the white matter of the cerebellum and areas adjacent to the fourth ventricle; the enzymes of the matrix metalloproteinases (MMPs) group, especially MMP-2 and MMP-9 have a key role in the myelin basic protein fragmentation and in demyelination, as well as in leukocyte traffic into the nervous milieu. To evaluate the involvement of MMPs during subacute distemper leukoencephalitis, we measured the levels of MMP-2 and MMP-9 by zymography in the cerebrospinal fluid (CSF) and in the cerebellum of 14 dogs naturally infected with CDV and 10 uninfected dogs. The infected dogs presented high levels of pro-MMP-2 in the CSF and elevated levels of pro-MMP-2 and pro-MMP-9 in the cerebellar tissue. Active MMP-2 was detected in the CSF of some infected dogs. As active MMP-2 and MMP-9 are required for cellular migration across the blood-brain barrier and any interference between MMPs and their inhibitors may result in an amplification of demyelination, this study gives additional support to the involvement of MMPs during subacute distemper leukoencephalitis and suggests that MMP-2 and MMP-9 may take part in the brain inflammatory changes of this disease.

Tissue inhibitor of metalloproteinase 1 is preferentially expressed in Th1 and Th17 T-helper cell subsets and is a direct STAT target gene

CD4(+) T helper (Th) cells differentiate into distinct effector subsets that are critical for host defense, but are also implicated in the pathogenesis of autoimmune disorders. Thelper17 (Th17) cells in particular are emerging as important drivers of multiple diseases including psoriasis, spondyloarthropathy and multiple sclerosis. To gain insight into the function of Th17 cells, we performed transcriptional profiling in hopes of elucidating products not previously recognized as being functionally relevant in these T cells. Herein, we demonstrate that tissue inhibitor of metalloproteinase 1 (TIMP1), a secreted protein with pleiotropic effects on cellular growth, survival and integrity of the extracellular matrix, is preferentially produced by Th17 and Th1 cells. We further show that Th1 and Th17 cell TIMP1 regulation follows separate mechanisms with a requirement for STAT4 in the former and STAT3 in the latter. Finally, we demonstrate that when restricted to T cells, expression of TIMP1 promotes neuropathology in experimental allergic encephalomyelitis.

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.

Marked relationship between matrix metalloproteinase 7 and brain atrophy in HIV infection

Circulating levels of matrix metalloproteinases (MMP-1 and 7) have been found to correlate with the severity of brain injury in HIV-infected subjects. This study used high-resolution neuroanatomic imaging and automated segmentation algorithms to clarify this relationship. Both metalloproteinases were significantly correlated with increased cerebrospinal fluid volume fraction. Comprehensive brain volumetric analysis revealed a more marked relationship with atrophy for MMP-7, which was significantly correlated with neural injury in multiple brain regions and nearly all ventricular measurements. MMP-7 was also correlated with measures of virologic and cognitive status.

Serum matrix metalloproteinase levels correlate with brain injury in human immunodeficiency virus infection

Circulating levels of specific matrix metalloproteinases (MMPs; 1 and 7) were evaluated as correlates of brain injury in eight individuals in advanced human immunodeficiency virus (HIV) infection. Neurological status was quantified in vivo with automated segmentation algorithms and with diffusion tensor imaging. Both metalloproteinases correlated with microstructural brain alterations and the degree of atrophy. MMPs may influence neurological outcome through involvement in neuroimmune response, blood-brain barrier permeability, leukocyte migration, and MMP-mediated neurotoxicity.

Cleavage of osteopontin by matrix metalloproteinase-12 modulates experimental autoimmune encephalomyelitis disease in C57BL/6 mice

A role for osteopontin (OPN) in promoting disease activity of multiple sclerosis or its animal model experimental autoimmune encephalomyelitis (EAE) has recently been suggested. As the biological activity of OPN is heavily influenced by posttranslational processing, we investigated the capacity of matrix metalloproteinase (MMP)-12 to cleave OPN and determined whether this influenced disease activity. We found that OPN mRNA and protein expression in the spinal cord increased with EAE disease in C57BL/6 mice concurrently with MMP-12 expression. A Western blot of EAE and control spinal cords revealed different OPN-immunoreactive bands, with a pattern that was similar to MMP-12 cleavage of recombinant OPN in vitro. In addition, OPN fragments in the spinal cord of EAE-afflicted mice were reduced in MMP-12(-/-) mice compared with wild-type controls. However, examination of OPN(-/-) mice in short- and long-term experiments revealed no difference in EAE outcomes from wild-type animals. OPN/MMP-12 double null mice were generated, and it was revealed that MMP-12(-/-) mice had a worsening of disease compared with wild-type mice, which returned to wild-type levels in the OPN/MMP-12 double null mice. These results suggest that EAE disease activity may be modulated by the cleavage of OPN by MMP-12.

Pathway-focused arrays reveal increased matrix metalloproteinase-7 (matrilysin) transcription in trachomatous trichiasis

PURPOSE

Several genes that are associated with protection from or susceptibility to trachomatous trichiasis (TT) have been identified through genetic association studies. Yet there have been few studies in which gene expression profiles were assessed in TT cases and disease-free controls. The purpose was to identify genes that are differentially expressed in the upper tarsal conjunctiva of subjects with TT.

METHOD

Pathway-focused gene arrays were used to screen conjunctival RNA expression of 226 gene transcripts of interest. The screening was followed by validation of differentially expressed genes by qRT-PCR on an independent set of samples. Three different techniques were then used to test for quantitative differences in the recovered conjunctival protein fraction.

RESULTS

Focused arrays identified a set of 13 differentially expressed genes. Validation by qRT-PCR confirmed differential expression in four of these genes (COL1A1, COL7A1, MMP7, and TLR6). Increased expression of MMP7 was the only consistent differentially regulated gene in the conjunctival samples of trichiasis subjects. MMP7 was present in isolated conjunctival proteins and in the tissue culture supernatants of peripheral blood lymphocytes after stimulation.

CONCLUSIONS

There is an imbalance in extracellular matrix turnover with minimal contribution of adaptive immune responses at this stage of trichiasis. There was little evidence of broad differential expression in genes characteristic of polar responses of adaptive T cells or macrophages. The control of the MMP7 response and its activity appears significant in the fibrotic changes observed in TT.

Matrix metalloproteinase processing of CXCL11/I-TAC results in loss of chemoattractant activity and altered glycosaminoglycan binding

The CXCR3 chemokine receptor regulates the migration of Th1 lymphocytes and responds to three ligands: CXCL9/MIG, CXCL10/IP-10, and CXCL11/I-TAC. We screened for potential regulation of T cell responses by matrix metalloproteinase (MMP) processing of these important chemokines. The most potent of the CXCR3 ligands, CXCL11, was identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry as a substrate of the PMN-specific MMP-8, macrophage-specific MMP-12, and the general leukocyte MMP-9. The 73-amino acid residue CXCL11 is processed at both the amino and carboxyl termini to generate CXCL11-(5-73), -(5-63), and -(5-58) forms. NH2-terminal truncation results in loss of agonistic properties, as shown in calcium mobilization and chemotaxis experiments using CXCR3 transfectants and human T lymphocytes. Moreover, CXCL11-(5-73) is a CXCR3 antagonist and interestingly shows enhanced affinity to heparin. However, upon COOH-terminal truncation to position 58 there is loss of antagonist activity and heparin binding. Together this highlights an unexpected site for receptor interaction and that the carboxyl terminus is critical for glycosaminoglycan binding, an essential function for the formation of chemokine gradients in vivo. Hence, MMP activity might regulate CXCL11 tissue gradients in two ways. First, the potential of CXCL11-(5-73) to compete active CXCL11 from glycosaminoglycans might lead to the formation of an antagonistic haptotactic chemokine gradient. Second, upon further truncation, MMPs disperse the CXCL11 gradients in a novel way by proteolytic loss of a COOH-terminal GAG binding site. Hence, these results reveal potential new roles in down-regulating Th1 lymphocyte chemoattraction through MMP processing of CXCL11.

Matrix metalloproteinase-3 induction in rat brain astrocytes: focus on the role of two AP-1 elements

Many brain cells secrete MMPs (matrix metalloproteinases), and increased or misregulated MMP levels are found in neurodegenerative disorders. Here we report that MMP-3 transcription and protein secretion were increased in rat brain astrocytes stimulated with lipopolysaccharide, gangliosides or interferon-gamma. Sequential deletion of the MMP-3 promoter revealed that sequences between -0.5 kb and the start codon were crucial for the transcriptional induction of MMP-3. In addition, experiments using pharmacological inhibitors of individual mitogen-activated protein kinases revealed that MMP-3 induction and promoter activity involved Jun N-terminal kinase, a representative upstream signal of AP-1 (activator protein-1). Sequence analyses of the region of the MMP-3 promoter 500 bp from the start codon indicated the presence of three AP-1 binding sequences. Among them, electrophoretic-mobility-shift assays as well as site-directed mutagenesis of individual AP-1 sequences revealed that distal and middle, but not proximal, sequences largely mediated its induction. Together, these results indicate that AP-1 could control MMP-3 induction in brain astrocytes and that its regulation through specific AP-1 elements could be exploited in the treatment of brain pathologies in which increased expression of MMP-3 plays crucial roles.

Association of the MMP-3 5A/6A gene polymorphism with multiple sclerosis in patients from Serbia

Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in remodeling of the extracellular matrix. MMPs are suggested to play a role in the influx of inflammatory cells into the CNS, disruption of the blood brain barrier, and to degrade myelin in vitro. In this study, we have investigated the possible association of MMP-3 5A/6A gene polymorphism with MS susceptibility and/or severity in patients from Serbia. A total of 184 MS patients (150 RR, 34 SP) and 236 controls have been studied. Results show that the distribution of MMP-3 5A/6A genotype frequencies between MS patients and controls were not significantly different. In bout onset patients, carriers of MMP-3 6A/6A genotype had significantly higher mean MSSS values compared to the carriers of 5A allele (6.29+/-1.89 vs. 5.29+/-2.62, respectively, ANCOVA, p=0.01 Scheffe post-hoc test). In conclusion, our results indicate association of MMP-3 6A/6A genotype with significantly higher mean MSSS values. Thus, the obtained results suggest that it should be carefully considered during follow up of patients with MS. Further genetic and functional studies are needed to resolve the complex role of MMPs and their tissue inhibitors in MS pathology and/or regeneration.

Elevation of matrix metalloproteinases (MMPs) in multiple sclerosis and impact of immunomodulators

The matrix metalloproteinases (MMPs) are implicated in the pathology of multiple sclerosis (MS). This review summarizes the consequences of upregulation of MMP members in MS as well as in an animal model of the disease, experimental autoimmune encephalomyelitis (EAE). The pathogenic roles of MMPs are considered, especially in the transmigration of leukocytes into the CNS. We review the evidence that interferon-beta, an immunomodulator that is commonly used in MS, affects MMP expression in the disease. The potential of minocycline as a therapy in MS, based on its activity as an MMP inhibitor, is discussed. Besides affecting MMPs, minocycline may have other actions that help account for its possible utility in MS.

Dendritic cell transmigration through brain microvessel endothelium is regulated by MIP-1alpha chemokine and matrix metalloproteinases

Dendritic cells (DCs) accumulate in the CNS during inflammatory diseases, but the exact mechanism regulating their traffic into the CNS remains to be defined. We now report that MIP-1alpha increases the transmigration of bone marrow-derived, GFP-labeled DCs across brain microvessel endothelial cell monolayers. Furthermore, occludin, an important element of endothelial tight junctions, is reorganized when DCs migrate across brain capillary endothelial cell monolayers without causing significant changes in the barrier integrity as measured by transendothelial electrical resistance. We show that DCs produce matrix metalloproteinases (MMP) -2 and -9 and GM6001, an MMP inhibitor, decreases both baseline and MIP-1alpha-induced DC transmigration. These observations suggest that DC transmigration across brain endothelial cell monolayers is partly MMP dependent. The migrated DCs express higher levels of CD40, CD80, and CD86 costimulatory molecules and induce T cell proliferation, indicating that the transmigration of DCs across brain endothelial cell monolayers contributes to the maintenance of DC Ag-presenting function. The MMP dependence of DC migration across brain endothelial cell monolayers raises the possibility that MMP blockers may decrease the initiation of T cell recruitment and neuroinflammation in the CNS.

Loss of flow induces leukocyte-mediated MMP/TIMP imbalance in dynamic in vitro blood-brain barrier model: role of pro-inflammatory cytokines

There is substantial evidence linking blood-brain barrier (BBB) failure during cerebral ischemia to matrix metalloproteinases (MMP). BBB function may be affected by loss of shear stress under normoxia/normoglycemia, as during cardiopulmonary bypass procedures. The present study used an in vitro flow-perfused BBB model to analyze the individual contributions of flow, cytokine levels, and circulating blood leukocytes on the release/activity of MMP-9, MMP-2, and their endogenous inhibitors, the tissue inhibitors of MMPs (TIMPs), TIMP-1, and TIMP-2. The presence of circulating blood leukocytes under normoxic/normoglycemic flow cessation/reperfusion significantly increased the luminal levels of MMP-9 and activity of MMP-2, accompanied by partial reduction of TIMP-1, complete reduction of TIMP-2 and increased BBB permeability. These changes were not observed during constant flow with circulating blood leukocytes, or after normoxic/normoglycemic or hypoxic/hypoglycemic flow cessation/reperfusion without circulating blood leukocytes. The addition of anti-IL-6 or anti-TNF-α antibody in the lumen before reperfusion suppressed the levels of MMP-9 and activity of MMP-2, had no effect on TIMP-1, and completely restored TIMP-2 and BBB integrity. Injection of TIMP-2 in the lumen before reperfusion prevented the activation of MMP-2 and BBB permeability. These data indicate that blood leukocytes and loss of flow are major factors in the activation of MMP-2, and that cytokine-mediated differential regulation of TIMP-1 and TIMP-2 may contribute significantly to BBB failure.

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.

PECAM-1 and gelatinase B coexist in vascular cuffs of multiple sclerosis lesions

In multiple sclerosis (MS), the matrix metalloprotease (MMP) gelatinase B/MMP-9 and platelet endothelial cell adhesion molecule (PECAM)-1 have both been implicated in trans-endothelial infiltration of leucocytes into the brain, but their functional connection has not yet been investigated. We investigated the expression of gelatinase B and PECAM-1 in post mortem brains of MS patients by immunohistochemistry. Because increased soluble PECAM-1 serum levels have been observed in MS patients, we also tested in vitro whether this could be due to cleavage of PECAM-1 by gelatinase B or matrilysin-1/MMP-7. Constitutive expression of PECAM-1 was found on brain endothelial cells, whilst in active MS lesions cell-bound PECAM-1 was highly up-regulated on foamy macrophages in perivascular infiltrates and co-localized with gelatinase B. However, human THP-1 monocyte-bound or soluble recombinant PECAM-1 were both resistant to proteolytic cleavage by gelatinase B or matrilysin-1 in vitro, as demonstrated by Western blot analysis and flow cytometry. These results suggest that PECAM-1 and gelatinase B may complement each other during the transmigration of the blood-brain barrier by mononuclear cells.

Up-regulation of mRNA for matrix metalloproteinases-9 and -14 in advanced lesions of demyelinating canine distemper leukoencephalitis

Matrix metalloproteinases (MMPs) comprise a family of proteolytic zinc- and calcium-dependent enzymes that are capable of disrupting the blood-brain barrier and mediating the destruction of extracellular matrix and myelin components. MMPs are also involved in facilitating leukocyte migration into inflammatory sites of the central nervous system. To determine the cellular localization and the amount of mRNA for MMP-9, MMP-14 and a tissue inhibitor of metalloproteinases (TIMP-1) in dogs with spontaneous demyelinating distemper encephalitis, formalin-fixed paraffin-embedded cerebella were investigated by in situ hybridization using specific digoxigenin-labeled RNA probes. Additionally, immunohistochemistry was performed to characterize the different types of plaques of demyelinating leukoencephalitis. Furthermore, virus antigen and mRNA were detected by immunohistochemistry and in situ hybridization. Healthy control dogs revealed a weak signal for mRNA for MMP-9, MMP-14, and TIMP-1 in various numbers of neurons, astrocytes, microglial cells and oligodendrocytes. In the cerebella of dogs with distemper, a strong increase of both number and staining intensity of MMP-9, MMP-14, and TIMP-1 mRNA-expressing cells, mainly in subacute inflammatory lesions and chronic plaques, was observed. The number of cells expressing mRNA for MMP-9 and MMP-14 increased about two- to threefold compared to TIMP-1 mRNA-expressing cells, whereas staining intensity of individual cells was similar. In early lesions, especially astrocytes and activated macrophages/microglial cells displayed a positive signal for MMPs and TIMP-1, whereas in older lesions activated microglia/macrophages and infiltrating lymphocytes represented the main source for MMP-9, MMP-14, and TIMP-1 mRNA synthesis as revealed by double-labeling techniques. In summary, the proportionally higher increase of MMP mRNA-expressing cells might indicate an MMP/TIMP imbalance as a cause for lesion initiation and progression in demyelinating canine distemper leukoencephalitis.

Genetic association between polymorphisms in the ADAMTS14 gene and multiple sclerosis

ADAMTS14 is a novel member of the ADAMTS (a disintegrin-like and metalloproteinase domain with thrombospondin type 1 modules) metalloproteinase family which processes extracellular matrix proteins. In the present study we performed a comprehensive investigation of the ADAMTS14 as a candidate gene for susceptibility to multiple sclerosis (MS). Eight single nucleotide polymorphisms (SNPs) were analyzed in a case-control study of 287 patients with MS [192 with relapsing-remitting MS (RRMS) and 95 with primary-progressive MS (PPMS)], and 285 age- and sex-matched controls. Allele and genotype frequencies were compared between controls and the MS subgroups, and gene-based haplotypes were reconstructed by computational procedures. Pairwise linkage disequilibrium values (D') suggested that three locus pairs (SNPs 3 through 5) had alleles in strong disequilibrium and constituted a haplotype block spanning 14 kb. Overall comparisons of allele and genotype frequencies showed association for SNPs 3 and 6 with MS. Stratification of MS patients according to major clinical forms revealed an increased frequency of both allele C (p = 0.006) and CC homozygosity (p = 0.008) at SNP6 in RRMS patients compared with controls. PPMS was associated with allele A at SNP2 compared with RRMS (p = 0.003) and controls (p = 0.009), and with CG heterozygosity at SNP3 compared with controls (p = 0.005). Haplotype frequency comparisons showed significant association between PPMS and the AGGGC haplotype compared with controls (p = 0.0004), and negative association between RRMS and the GGAGT haplotype compared with controls (p = 0.0026). No association was detected between different genotypes and disease severity measured by the Multiple Sclerosis Severity Score (MSSS). These findings suggest a potentially important role for the ADAMTS14 gene in predisposition to MS.

Decreased MMP-9 production in primary progressive multiple sclerosis patients

BACKGROUND

An increase in MMP-9 levels has been found in relapsing-remitting (RR) multiple sclerosis (MS) showing correlation with magnetic resonance (MR) parameters mainly during relapses. However, data regarding primary progressive (PP) MS is scarce.

OBJECTIVES

To determine both the pro and active forms of MMP-9 in PPMS and transitional progressive (TP) MS, RRMS and healthy controls (HC), and to assess the relationship between MMP-9 levels and clinical and radiological variables in PP/TPMS.

METHODS

73 patients with PP/TPMS, 50 RRMS and 43 HC were studied. Levels of pro and active forms of MMP-9 in serum were measured with ELISA. EDSS and MSFC scores were recorded and T2- and T1-weighted MR scans were obtained at the time of blood sampling and one and two years later for PP/TP MS cases.

RESULTS

MMP-9 levels were 202.27 ng/ml for PP/TPMS, 242.20 ng/ml for RRMS and 274.49 ng/ml for HC. MMP-9 levels were significantly lower in PP/TPMS compared to RRMS (P= 0.026) and HC (P= 0.001). No significant correlations were found between MMP-9 levels and clinical scores or radiological parameters.

CONCLUSIONS

These results point to different regulatory mechanisms of MMP-9 production and/or activity between PP/TPMS and RRMS.

Capacity of Epstein-Barr virus to infect monocytes and inhibit their development into dendritic cells is affected by the cell type supporting virus replication

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that is involved in the pathogenesis of a wide spectrum of malignant and non-malignant diseases. Strong evidence implicates T lymphocytes in the control of EBV replication and tumorigenesis, but cellular components of the innate immune system are poorly characterized in terms of their function in the development of EBV-specific immunity or interaction with the virus. This study demonstrates that EBV virions produced in epithelial cells surpass their B cell-derived counterparts in the capacity to enter monocytes and inhibit their development into dendritic cells (DCs). Different ratios of the gp42 and gH glycoproteins in the envelope of virions that were derived from major histocompatibility complex class II-positive or -negative cells accounted primarily for the differences in EBV tropism. EBV is shown to enter both monocytes and DCs, although the cells are susceptible to virus-induced apoptosis only if infected at early stages of DC differentiation. The purified gH/gL heterodimer binds efficiently to monocytes and DCs, but not to B cells, suggesting that high expression levels of a putative binding partner for gH contribute to virus entry. This entry takes place despite very low or undetectable expression of CD21, the canonical EBV receptor. These results indicate that the site of virus replication, either in B cells or epithelial cells, alters EBV tropism for monocytes and DCs. This results in a change in the virus's immunomodulating capacity and may have important implications for the regulation of virus-host interactions during primary and chronic EBV infection.

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.

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.

Serum MMP-2 and MMP-9 are elevated in different multiple sclerosis subtypes

In multiple sclerosis (MS), matrix metalloproteinase (MMP) activity in tissues is the result of a balance between MMPs and their tissue inhibitors (TIMPs). MMP-9 predominates in acute MS lesions and is inhibited by TIMP-1, while MMP-2 may participate in the remodeling of the extracellular matrix (ECM) such as in chronic disease and is inhibited by TIMP-2. These differences may be reflected in serum and cerebrospinal fluid (CSF). We have tried to characterize MMP-2 and MMP-9 activities, in relation to their respective TIMPs, 2 and 1, as a factor of different types of the disease, as this information was not previously clearly stated. We found the MMP-2/TIMP-2 ratio in serum to show higher values in secondary progressive (SP, p=0.02) and primary progressive (PP, p=0.01) MS than short disease duration (SDD) relapsing-remitting (RR) MS, but not different from the healthy control (HC) group. Whereas the MMP-9/TIMP-1 ratio in serum showed higher (p=0.04) values in SDD RR MS than PP but also in active patients, evaluated either clinically (p=0.006) or from the magnetic resonance imaging (MRI, p<0.05), compared to inactive disease. CSF MMP to TIMP ratios did not differ between MS subtypes, suggesting systemic rather CNS-restricted changes. These results show that an increase in MMP-2/TIMP-2 ratio marks chronic progression in MS, but it is as high as in HC, and also confirm that high MMP-9 activity characterizes short duration relapsing and active forms of the disease.

Trypsin-sensitive and lipid-containing sites of the macrophage extracellular matrix bind apolipoprotein A-I and participate in ABCA1-dependent cholesterol efflux

A unique property of the extracellular matrix of J774 and THP-1 cells has been identified, which contributes to the ability of these cells to promote cholesterol efflux. We demonstrate high level apolipoprotein (apo) A-I binding to macrophage cells (THP-1 and J774) and to their extracellular matrix (ECM). However, high level apoA-I binding is not observed on fibroblasts, HepG2 cells, or U937 cells (a macrophage cell line that does not efflux cholesterol to apoA-I or bind apoA-I on their respective ECM). Binding to the ECM of THP-1 or J774 macrophages depends on the presence of apoA-I C-terminal helices and is markedly reduced with a mutant lacking residues 187-243 (apoA-I Delta(187-243)), suggesting that the hydrophobic C terminus forms a hydrophobic interaction with the ECM. ApoA-I binding is lost upon trypsin treatment or with Triton X-100, a preparation method that de-lipidates the ECM. However, binding is recovered with re-lipidation, and is preserved with ECM prepared using cytochalasin B, which conserves the endogenous phospholipid levels of the ECM. We also demonstrate that specific cholesterol efflux to apoA-I is much reduced in cells released from their native ECM, but fully restored when ECM-depleted cells are added back to ECM in the presence of apoA-I. The apoA-I-mediated efflux is deficient in plated or suspension U937 macrophages, but is restored to high levels when the suspension U937 cells are reconstituted with the ECM of J774 cells. The ECM-dependent activity was much reduced in the presence of glyburide, indicating participation of ABCA1 (ATP-binding cassette transporter 1) in the efflux mechanism. These studies establish a novel binding site for apoA-I on the macrophage ECM that may function together with ABCA1 in promoting cholesterol efflux.

Monocyte-derived dendritic cells express and secrete matrix-degrading metalloproteinases and their inhibitors and are imbalanced in multiple sclerosis

Dendritic cells (DC) are antigen-presenting cells (APC) that most efficiently initiate and control immune responses. Migration processes of blood DC are crucial to exert their professional antigen-presenting functions. Matrix-degrading metalloproteinases (MMP) are proteolytic enzymes, which are considered to be key enzymes in extracellular matrix (ECM) turnover and mediators of cell migration. Tissue inhibitors of metalloproteinases (TIMP) are important regulators of MMP activity. Here we investigate whether blood monocyte-derived immature DC (iDC) and mature DC (mDC) express, produce and secrete functionally active MMP-1, -2, -3 and -9 and their inhibitors TIMP-1 and -2, and examine their involvement in multiple sclerosis (MS). On mRNA level, we observed high numbers of MMP-2 and TIMP-2 mRNA expressing iDC in MS. On protein level, high percentages of MMP-1, -2 and -9 expressing iDC by flow cytometry, and high MMP-1 secretion by Western blot together with high MMP-2 and -9 activities in iDC supernatants as studied with zymography were observed. Similarly, MS is associated with high percentages of MMP-2 and -3 and of TIMP-1 expressing mDC by flow cytometry together with high MMP-3 secretion and high MMP-9 activity in culture supernatants. Spontaneous migratory capacity of both iDC and mDC over ECM-coated filters was higher in MS compared to healthy controls (HC). In conclusion, blood monocyte-derived iDC and mDC express, produce and secrete several MMP and TIMP. Alterations in these molecules as observed in MS may be functionally important for DC functioning.

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

The matrix metalloproteinases (MMPs) are a family of endoproteinases that degrade various components of the extracellular matrix and have been implicated in the pathogenesis of multiple sclerosis. To determine whether up-regulation of MMP-3, or stromelysin-1, was a causative factor during the development of demyelination, we have examined the expression of MMP-3 mRNA and protein in brain tissue of a spontaneously demyelinating mouse model overexpressing DM20 (ND4 line) prior to and during the progression of disease. Stromelysin-1, but not other MMP mRNA was elevated approximately 10-fold in transgenic mice between 5 days and 1 month of age, more than 2 months before the onset of disease, and was coordinately expressed with the DM20 transgene. Stromelysin-1 protein levels were also up-regulated as was tissue inhibitor of metalloproteinase-1 (TIMP-1), an in vivo regulator of stromelysin-1 mRNA. When we crossed our ND4 mice with a line of transgenic mice overexpressing TIMP-1 in brain, clinical signs in these mice were attenuated, and the level of stromelysin-1 protein was reduced. Thus, in this transgenic model of demyelinating disease up-regulation of DM20, MMP-3, and TIMP-1 represent important changes in the chemical pathogenesis in brain, which precede the onset of disease.