Matrix metalloproteinases in inflammatory myopathies: enhanced immunoreactivity near atrophic myofibers

OBJECTIVES: To further examine the role of proteolytic enzyme expression of matrix metalloproteinases (MMP) and T-cell markers in inflammatory myopathies and controls. MATERIAL AND METHODS: We studied the expression of MMP-2, MMP-7, and MMP-9 in 19 cases of inflammatory myopathies and controls using immunocytochemistry. RESULTS: Inflammatory myopathies showed distinct patterns of up-regulation of MMP. MMP-9 was strongly expressed in atrophic myofibers in all inflammatory myopathies. MMP-2 immunoreactivity was similar in its distribution, however, to a weaker intensity. In dermatomyositis the perifascicular atrophy showed pronounced MMP-9 immunoreactivity, probably reflecting denervated patterns of myofibers. Moreover, MMP-7 strongly immunolabeled invaded myofibers in polymyositis cases only. CONCLUSION: These patterns confirm, that MMP-7 up-regulation is prominent in PM, while MMP-2 immunoreactivity is only slightly elevated in inflamed muscle. In general, MMP-9 up-regulation appears to be an important additional molecular event in the multistep process of all inflammatory myopathies.     

Matrix metalloproteinases and skeletal muscle: a brief review

Matrix metalloproteinases (MMPs) are a family of zinc- dependent proteolytic enzymes that function mainly in the extracellular matrix, where they contribute to the development, functioning, and pathology of a wide range of tissues. This mini-review describes the MMPs and tissue inhibitors of MMPs (TIMPs) in skeletal muscle, and considers their involvement in muscle development, ischemia, myonecrosis, angiogenesis, denervation, exercise-induced injuries, disuse atrophy, muscle repair and regeneration, and inflammatory myopathies and dystrophies. Despite the very limited information currently available on MMPs and their inhibitors in skeletal muscle, it is becoming increasingly clear that they have important physiological functions in maintenance of the integrity and homeostasis of muscle fibers and of the extracellular matrix. Understanding the roles of MMPs and TIMPs may lead to the development of new drug-related treatments for various muscle disorders based on suppression or upregulation of their expression.     

Matrix metalloproteinases in neuroinflammation

Matrix metalloproteinases (MMPs) are a gene family of neutral proteases that are important in normal development, wound healing, and a wide variety of pathological processes, including the spread of metastatic cancer cells, arthritic destruction of joints, atherosclerosis, and neuroinflammation. In the central nervous system (CNS), MMPs have been shown to degrade components of the basal lamina, leading to disruption of the blood-brain barrier (BBB), and to contribute to the neuroinflammatory response in many neurological diseases. Brain cells express both constitutive and inducible MMPs in response to cellular stress. MMPs are tightly regulated to avoid unwanted proteolysis. Secreted as inactive enzymes, the MMPs require activation by other proteases and free radicals. The MMPs are part of a larger class of metalloproteinases (MPs), which includes the recently discovered ADAMs (a disintegrin and metalloproteinase domain) and ADAMTS (a disintegrin and metalloproteinase thrombospondin) families. MPs have complex roles at the cell surface and within the extracellular matrix. At the cell surface, they act as sheddases, releasing growth factors, death receptors, and death-inducing ligands, making them important in cell survival and death. Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that regulate the activity of the MMPs. Synthetic inhibitors have been developed for the treatment of arthritis and cancer. These hydroxymate-based compounds have been shown to reduce injury in experimental allergic encephalomyelitis (EAE), experimental allergic neuritis (EAN), cerebral ischemia, intracerebral hemorrhage, and viral and bacterial infections. MPs have both beneficial and detrimental roles; understanding their expression in various CNS insults will allow for the use of MMP inhibitors in the treatment of neurological disorders.     

Extracellular matrix and matrix metalloproteinases in sciatic nerve

Although matrix metalloproteinases (MMPs) are increasingly being implicated in several pathologies of the nervous system, it is not yet clear what role they play in normal neurobiological processes. We review the expression of extracellular matrix (ECM) components as well as MMPs and tissue inhibitors of metalloproteinases (TIMPs) in the peripheral nervous system. We explore the expression of certain MMPs and the four TIMPs at the mRNA level in the postnatal mouse sciatic nerve. In addition, we have used substrate gel and in situ zymography to determine levels of MMP-2 and -9 and TIMP activity in rat sciatic nerve after crush and during regeneration. A rapid and transient increase in MMP-9 localised at and immediately distal to the site of injury was observed, whereas an increase in MMP-2 activity was delayed, prolonged, and extended proximal and distal to the injury site. This activity coincides with periods of axonal elongation, suggesting that it could act to facilitate axonal extension along the nerve matrix. We also detected multiple species of gelatinolytic inhibitory activity, including TIMP-1 and -3 in control and injured nerve. These activities probably act to prevent uncontrolled gelatinolytic activity, maintaining nerve integrity at the level essential for axonal regrowth.     

Matrix metalloproteinases in neuromuscular disease

Matrix metalloproteinases (MMPs), a family of zinc-dependent endoproteinases, are effector molecules in the breakdown of the blood-brain and blood-nerve barrier, and promote neural tissue invasion by leukocytes in inflammatory diseases of the central and peripheral nervous systems. Moreover, MMPs play an important role in synaptic remodeling, neuronal regeneration, and remyelination. Recent work concerning MMPs in patients with neuropathy, myopathy, spinal cord injury, and amyotrophic lateral sclerosis (ALS), and in corresponding animal models, is discussed in this review.     

MMP、TIMP在颅内动脉瘤中表达的实验研究

目的 本研究探讨基质金属蛋白酶(MMP)及基质金属蛋白酶抑制剂在颅内动脉瘤中的基因表达及作用.方法 将30例颅内动脉瘤患者分为破裂动脉瘤组及未破裂动脉瘤组,均开颅行夹闭术,术后获得动脉瘤标本,real time RT-PCR法定量测定MMPs、TIMPs mRNA水平.ELISA法测定破裂动脉瘤与未破裂动脉瘤患者血清中MMP-2、MMP-9水平.免疫组织化学染色定位MMP、TIMP在组织细胞的位置.结果 与未破裂动脉瘤相比,MMP-2、MMP-9在破裂动脉瘤中明显升高(P＜0.05),MMP-2/TIMP-1,MMP-2/TIMP-2,MMP-2/TIMP-3,MMP-9/TIMP-2在破裂动脉瘤中明显升高(P＜0.05).破裂动脉瘤患者血清MMP-2、MMP-9水平明显高于未破裂动脉瘤(P＜0.05).结论 破裂和未破裂动脉瘤之间MMP表达水平差异与动脉瘤破裂相关.     

Matrix metalloproteinases are involved in mechanical stretch-induced activation of skeletal muscle satellite cells

When skeletal muscle is stretched or injured, myogenic satellite cells are activated to enter the cell cycle. This process depends on nitric oxide (NO) production, release of hepatocyte growth factor (HGF) from the extracellular matrix, and presentation of HGF to the c-met receptor. Experiments reported herein provide new evidence that matrix metalloproteinases (MMPs) are involved in the NO-dependent release of HGF in vitro. When rat satellite cells were treated with 10 ng/ml recombinant tissue inhibitor-1 of MMPs (TIMP-1) and subjected to treatments that induce activation in vitro, i.e., sodium nitroprusside (SNP) of an NO donor or mechanical cyclic stretch, the activation response was inhibited. In addition, conditioned medium generated by cultures treated with TIMP-1 plus SNP or mechanical stretch failed to activate cultured satellite cells and did not contain HGF. Moreover, NO(x) assay demonstrated that TIMP-1 does not impair NO synthase activity of stretched satellite cell cultures. Therefore, results from these experiments provide strong evidence that MMPs mediate HGF release from the matrix and that this step in the pathway is downstream from NO synthesis.     

Matrix metalloproteinases and proteoglycans in axonal regeneration

After an injury to the adult mammalian central nervous system (CNS), a variety of growth-inhibitory molecules are upregulated. A glial scar forms at the site of injury and is composed of numerous molecular substances, including chondroitin sulfate proteoglycans (CSPGs). These proteoglycans inhibit axonal growth in vitro and in vivo. Matrix metalloproteinases (MMPs) can degrade the core protein of some CSPGs as well as other growth-inhibitory molecules such as Nogo and tenascin-C. MMPs have been shown to facilitate axonal regeneration in the adult mammalian peripheral nervous system (PNS). This review will focus on the various roles of proteoglycans and MMPs within the injured nervous system. First, we will present a general background on the injured central nervous system and explore the roles that proteoglycans play in the injured PNS and CNS. Second, we will discuss the various functions of MMPs within the injured PNS and CNS. Special attention will be paid to the possibility of how MMPs might modify the growth-inhibitory extracellular environment of the injured adult mammalian spinal cord and facilitate axonal regeneration in the CNS.     

Neurospheres: insights into neural stem cell biology

Neural stem cells (NSC) are a tissue-specific subtype of self-renewing and multipotent cells that can give rise to all neural populations. In this review, the importance of maintaining cell-cell contacts in the study of NSC is highlighted, and data obtained from some crucial single-cell studies is compared to results obtained from neurospheres, where aggregates of NSC are grown in suspension. In particular, results that indicate how this culture system may be well suited to analyze NSC plasticity, cell-cell, and cell-extracellular matrix (ECM) interactions are pointed out, and the hypothesis that cell-cell and cell-ECM contacts may be essential for NSC maintenance, survival, and proliferation is highlighted. Finally, it is suggested that neurospheres might play a role in the study of context-dependent behavior of NSC in niches by providing a system where NSC can be challenged chemically or biologically and analyzed in vitro, in a time- and context-dependent manner.     

Matrix metalloproteinases and their tissue inhibitors in serum and cerebrospinal fluid of patients with amyotrophic lateral sclerosis

Background and purpose: Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). We investigated the expression of MMPs and tissue inhibitors of matrix metalloproteinases (TIMPs) in serum and cerebrospinal fluid (CSF) correlating the results with age, disease duration and the clinical course. Methods: The material consisted of 30 ALS patients and 15 age‐matched healthy controls. ELISA method to determine the expression of MT‐MMP‐1, MMP‐2, MMP‐9, TIMP‐1 and TIMP‐2 in serum and CSF was used. MMP‐2 and MMP‐9 by zymography was also tested. Results: In serum MT‐MMP‐1, MMP‐2, MMP‐9 and TIMP‐1 expression was increased, especially in mild ALS cases. TIMP‐2 values were normal. In CSF MT‐MMP‐1, MMP‐2 and TIMP‐1 level was either increased or normal, that of MMP‐9 was decreased. TIMP‐2 did not change. No correlation of MMPs and TIMP‐1 expression in serum and CSF and the age of the patients was found. A correlation was observed between MMPs and TIMPs and disease duration. Conclusions: Increased level of MMPs and TIMP‐1 of ALS patients may reflect the degeneration process of motor neurons and skeletal muscles and/or is associated with tissues remodeling. The low level of MMP‐9 in CSF may result from impaired balance between MMP‐9 and TIMP‐1 and/or its increased intrathecal degradation and physical clearance. Although the role of changed MMPs/TIMPs level in the pathogenesis of ALS is not clear their analysis in serum may be used as prognostic factor and a potential marker for monitoring treatment effects.     

Phase-dependent expression of matrix metalloproteinases and their inhibitors in demyelinating canine distemper encephalitis

Matrix metalloproteinases (MMPs) are zinc- and calcium-dependent enzymes that cleave molecules of the extracellular matrix, and thus are able to open the blood-brain-barrier and affect myelin. Their inhibitors (TIMPs) are important candidates for the therapy of demyelinating diseases. To establish an immunohistochemical profile of MMP and TIMP expression in plaque variants in dogs with spontaneous demyelinating distemper encephalitis, paraffin-embedded cerebella were studied employing the avidin-biotin-peroxidase complex method with a panel of nine polyclonal (anti-MMP-1, -3, -7, -9, -12, -13, -14, -TIMP-1, and -2) and two monoclonal antibodies (anti-latent MMP-2, and -MMP-11). All MMPs and TIMPs were prominently up-regulated in acute and subacute non-inflammatory lesions, and double-labeling techniques showed that they were mainly expressed by astrocytes and brain macrophages/microglia. In subacute inflammatory and chronic plaques, a moderate to strong decrease of MMP and TIMP expression compared to acute lesions was observed. In these phases MMP-11, -12, and -13 were still moderately present. In addition to astro- and microglia, invading perivascular mononuclear cells were positive for MMPs and TIMPs. In summary, there seems to be a phase-dependent expression of MMPs and TIMPs in demyelinating canine distemper encephalitis, and an MMP-TIMP imbalance might account for the lesion progression in this disease.     

Stimulation of adrenergic development in neural crest cultures by a reconstituted basement membrane-like matrix is inhibited by agents that elevate cAMP.

Previous work (Maxwell and Forbes: Development 101:767-776, 1987) has shown that an overlay of reconstituted basement membrane-like (RBM) gel dramatically increased the number of catecholamine-positive (CA+) cells which differentiated in neural crest cultures. We report here that this increase was inhibited when cultures were grown for 7 days in the presence of agents that elevate cAMP, such as 8-bromo-cAMP and 3-isobutyl-1-methylxanthine. The action of 8-bromo-cAMP was dose dependent with a half-maximal effect at about 50 microM. The development of CA+ cells was dramatically reduced when 8-bromo-cAMP was present from days 0-4 in vitro, but was relatively unaffected if 8-bromo-cAMP was present from days 4-7 in vitro. The development of tyrosine hydroxylase immunoreactive cells was also inhibited by 8-bromo-cAMP. The addition of 8-bromo-cAMP increased the number of melanocytes and resulted in either no change or only modest reductions in the number of E/C8 and neurofilament immunoreactive cells, indicating that the effect on CA+ cell ontogeny was selective. In contrast to the effect of 8-bromo-cAMP, addition of 8-bromo-cGMP did not inhibit CA+ cell development in the presence of the RBM gel nor did it stimulate CA+ cell development in the absence of the RBM gel overlay. Our results suggest that cAMP may be an important regulator of phenotypic expression in at least some neural crest cell lineages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reelin mRNA expression during embryonic brain development in the turtle Emys orbicularis.

The expression of reelin messenger ribonucleic acid (mRNA) was studied during embryonic brain development in the turtle Emys orbicularis, by using radioactive in situ hybridization. A high expression was consistently found in the olfactory bulb and in a few neurons in the marginal zone and, to a lesser extent, in the subplate of the dorsal and medial cortical sectors. In the diencephalon, the ventral division of lateral geniculate nuclei and the prospective reticular thalamic nuclei were strongly positive. High reelin signal was also associated with some layers of the tectum and with the external granule cell layer of the cerebellum. A more moderate signal was detected in the septal nuclei, striatum, dorsal ventricular ridge, retina, habenular nuclei, and hypothalamus, and in some reticular nuclei of the midbrain and hindbrain and in ventral spinal cord. The cortical plate, basal forebrain, amygdala, and tegmentum were weakly labeled. When they are compared to reelin expression during mammalian brain development, our data reveal an evolutionarily conserved canvas of reelin expression and significant differences, particularly in developing cortical fields. Most significantly, the developing turtle cortex does not display the heavy reelin expression in subpial Cajal-Retzius cells that is so typical of its mammalian counterpart. Given the key role of reelin in laminar cortical development, our data suggest that the increase in the number of reelin-producing cells and/or the amplification of reelin expression in the cortical marginal zone might have been a driving factor during the evolution of the laminated cerebral cortex from stem reptiles to mammals, as indicated in previous comparative analyses.     

Expression of a neurally related laminin binding protein by neural crest-derived cells that colonize the gut: relationship to the formation of enteric ganglia.

In order to give rise to the enteric nervous system (ENS), cells migrating from the neural crest must find the bowel and cease migrating at appropriate locations within the gut. Previous studies of the development of the ENS in a mutant mouse have led to the hypothesis that laminin in the enteric mesenchyme may act as a signal to crest-derived cells to cease migrating and extend neurites (or glial processes). Implied in this hypothesis is the idea that crest-derived cells, as a prelude to their participation in ganglion formation, acquire a neurally related laminin receptor, which they do not express at pre-enteric stages of migration. As a partial test of this hypothesis, single and double label immunocytochemistry at light and electron microscopic (EM) levels were used to study the expression of cell surface laminin binding proteins by crest-derived cells in the process of migrating to or within the developing chick gut. Two antibodies (called 3070 and alpha-110) raised against neuronal cell surface laminin binding proteins were employed for this purpose. Laminin binding protein immunoreactivity was found to be expressed within the bowel and ganglion of Remak by a subset of crest-derived cells (identified immunocytochemically with NC-1/HNK-1 antibodies) and by all of those developing as neurons (identified immunocytochemically with antibodies to neurofilament-associated proteins). Laminin binding protein immunoreactivity was also found to be expressed in fixed neural structures elsewhere in the embryos, including cranial and spinal roots, nerves, and ganglia. In contrast, laminin binding protein immunoreactivity was not expressed by migrating crest-derived cells in the vicinity of the vagal or sacral regions of the neuraxis (from which the precursors of the ENS take origin); nor was it expressed by juxta-pharyngeal vagal crest-derived cells migrating to the foregut through the caudal branchial arches or by the caudal stream of sacral crest-derived cells approaching the hindgut. EM immunocytochemistry confirmed that laminin binding protein immunoreactivity in the bowel was located on the surfaces of crest-derived cells, and was exhibited both by those cells that could only be distinguished from their neighbors by their NC-1/HNK-1 immunoreactivity and by cells developing as neurons or glia. EM immunocytochemistry also revealed that the surfaces of crest-derived cells migrating through the enteric mesenchyme were contacted by many small osmiophilic "puffs" of laminin-immunoreactive extracellular material. These puffs coincided in location with membrane sites that expressed the immunoreactivity of the laminin binding protein. These observations are consistent with the hypothesis that laminin plays a role in the formation of enteric ganglia.     

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

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

Matrix metalloproteinases MMP2 and MMP9 are upregulated by noradrenaline in the mouse neuroendocrine hypothalamus

Magnocellular neurons of the hypothalamic supraoptic nuclei (SON) are involved in the synthesis and release of two major neuropeptides: oxytocin (OT) and arginine-vassopressin (AVP). Neurochemical plasticity in this system is induced by physiological conditions such as lactation, parturition and dehydration, and may be accompanied by reversible structural plasticity affecting neurons, astrocytes and the extracellular matrix (ECM). The noradrenergic system plays a critical role in triggering this chemical plasticity associated with structural plasticity. Matrix metalloproteinases (MMPs) are good candidates for involvement in the ECM remodelling observed in structural plasticity. We investigated the possible regulation of the two gelatinases, MMP2 and MMP9, by noradrenaline (NA) in the mouse neuroendocrine hypothalamus. We looked for the presence, location and activity of MMP2 and MMP9 in the SON, using an ex vivo experimental model of mouse hypothalamic slices incubated for 4 h with 10⁻⁴  m NA. We showed that: (i) immunoreactivity for MMP2 and MMP9 was detected not only in AVP-positive and OT-positive magnocellular neurons, but also in astrocyte processes in control and NA-treated slices; (ii) the number of MMP2- and MMP9-positive cells increased after incubation with NA; (iii) MMP2 and MMP9 displayed markedly higher levels of gelatinolytic activity after NA treatment. These results suggest that both MMP2 and MMP9 are regulated by NA, and could therefore also be involved in structural plasticity within the SON.     

Chondroitin sulfate proteoglycans in the developing cerebral cortex: The distribution of neurocan distinguishes forming afferent and efferent axonal pathways

The pharmacological and physiological properties of ligand-gated ion channels are dependent on their subunit composition; spontaneously occurring changes in subunit composition during neuronal development may result in dramatic functional differences between embryonic and adult forms of the receptor complex. In the present study, in situ hybridization with antisense cRNA probes was used to examine the subunit composition of the γ-aminobutyric acid_A/benzodiazepine (GABA_A/BZ) receptor in the developing inferior olivary complex. This receptor is thought to be a pentameric chloride channel comprised of selected α, β, γ, δ, and ρ subunits, the majority of which have several isoforms: α_1?6, β_1?4, γ_1?4 and ρ_{1, 2}. Among the 13 subunit variants present in the mammalian central nervous system, α_2?5 β₃, and γ_{1, 2} mRNAs are expressed at significant levels in the inferior olivary complex. Two clearly different temporal patterns of GABA_A/BZ receptor subunit mRNA expression were observed: The expression of α₃, α₅, β₃, and γ₂ mRNAs was at a peak during embryonic and early postnatal development followed by rapid down-regulation thereafter. Conversely, α₂, α₄, and γ₁ mRNA expression was very low or absent during early development, and a pronounced increase was observed at the end of postnatal week 1. These studies suggest that there are developmental changes in the subunit composition of the GABA_A/BZ receptor in inferior olivary neurons. These changes in subunit expression, which occur during a period of major alterations in afferent and efferent synaptic connections, may subserve a change in the role of GABA from its function as a neurotrophic factor to that of an inhibitory neurotransmitter. © 1995 Wiley-Liss, Inc.     

Characterization of matrix metalloproteinases in denervated muscle

In a nerve crush model of denervation, we examined muscle matrix metalloproteinase (MMP) expression, localization and activity. In normal muscle, MMP mRNA levels were low, and immunohistochemically MMPs were distributed around the muscle fibre with MMPs-3, -7 and -9 also staining at the neuromuscular junction. Seven days after nerve crush, muscle MMP immunoreactivity, especially MMP-12 and MMP-14, became irregularly distributed. At 20 days reinnervation of the muscle was observed, and some restitution of the normal pattern of immunoreactivity was noted concomitant with a higher level of MMP mRNA expression. In situ zymography showed that MMP activity was very weak in normal muscle whereas it was increased up to 40 days following denervation. Our results suggest that MMPs in muscle are involved in the tissue changes following denervation. Further experiments are required to test the hypothesis that MMP inhibition may be beneficial in protecting muscle from excessive remodelling following denervation and therefore improve reinnervation.