Endogenous and synthetic MMP inhibitors in CNS physiopathology

Characterization of Angiogenic, Matrix Remodeling, and Antimicrobial Factors in Preterm and Full-Term Human Umbilical Cords

BACKGROUND

Little is known about morphogenetic changes in the umbilical cord during the maturation process. Extracellular matrix remodeling, angiogenesis, progenitor activity, and immunomodulation are represented by specific markers; therefore, the aim of this study was to determine the expression of matrix metalloproteinase-2 (MMP2), tissue inhibitor of metalloproteinases-2 (TIMP2), CD34, vascular endothelial growth factor (VEGF), and human β-defensin 2 (HBD2) in preterm and full-term human umbilical cord tissue.

METHODS

Samples of umbilical cord tissue were obtained from 17 patients and divided into two groups: very preterm and moderate preterm birth umbilical cords; late preterm birth and full-term birth umbilical cords. Routine histology examination was conducted. Marker-positive cells were detected using the immunohistochemistry method. The number of positive structures was counted semi-quantitatively using microscopy. Statistical analysis was carried out using the SPSS Statistics 29 program.

RESULTS

Extraembryonic mesenchyme cells are the most active cell producers, expressing MMP2, TIMP2, VEGF, and HBD2 at notable levels in preterm and full-term umbilical cord tissue. Statistically significant differences in the expression of CD34, MMP2, and TIMP2 between the two patient groups were found. The expression of VEGF was similar in both patient groups, with the highest number of VEGF-positive cells seen in the extraembryonic mesenchyme. The expression of HBD2 was the highest in the extraembryonic mesenchyme and the amniotic epithelium, where mostly moderate numbers of HBD2-positive cells were detected.

CONCLUSIONS

Extracellular matrix remodeling in preterm and term umbilical cords is strongly regulated, and tissue factors MMP2 and TIMP2 take part in this process. The expression of VEGF is not affected by the umbilical cord's age; however, individual patient factors can affect the production of VEGF. Numerous CD34-positive cells in the endothelium of the umbilical arteries suggest a significant role of progenitor cells in very preterm and moderate preterm birth umbilical cords. Antimicrobial activity provided by HBD2 is essential and constant in preterm and full-term umbilical cords.

Metal Complexes as Promising Matrix Metalloproteinases Regulators

Nowadays, cancers and dementia, such as Alzheimer's disease, are the most fatal causes of death. Many studies tried to understand the pathogenesis of those diseases clearly and develop a promising way to treat the diseases. Matrix metalloproteinases (MMPs) have been reported to be involved in the pathology of cancers and AD through tumor cell movement and amyloid degradation. Therefore, control of the levels and actions of MMPs, especially MMP-2 and MMP-9, is necessary to care for and/or cure cancer and AD. Various molecules have been examined for their potential application as regulators of MMPs expression and activity. Among the molecules, multiple metal complexes have shown advantages, including simple synthesis, less toxicity and specificity toward MMPs in cancer cells or in the brain. In this review, we summarize the recent studies and knowledge of metal complexes (e.g., Pt-, Ru-, Au-, Fe-, Cu-, Ni-, Zn-, and Sn-complexes) targeting MMPs and their potentials for treating and/or caring the most fatal human diseases, cancers and AD.

The tetrapartite synapse in neuropsychiatric disorders: Matrix metalloproteinases (MMPs) as promising targets for treatment and rational drug design

Inflammation and an exacerbated immune response are widely accepted contributing mechanisms to the genesis and progression of major neuropsychiatric disorders. However, despite the impressive advances in understanding the neurobiology of these disorders, there is still no approved drug directly linked to the regulation of inflammation or brain immune responses. Importantly, matrix metalloproteinases (MMPs) comprise a group of structurally related endopeptidases primarily involved in remodeling extracellular matrix (ECM). In the central nervous system (CNS), these proteases control synaptic plasticity and strength, patency of the blood-brain barrier, and glia-neuron interactions through cleaved and non-cleaved mediators. Several pieces of evidence have pointed to a complex scenario of MMPs dysregulation triggered by neuroinflammation. Furthermore, major psychiatric disorders' affective symptoms and neurocognitive abnormalities are related to MMPs-mediated ECM changes and neuroglia activation. In the past decade, research efforts have been directed to broad-spectrum MMPs inhibitors with frustrating clinical results. However, in the light of recent advances in combinatorial chemistry and drug design technologies, specific and CNS-oriented MMPs modulators have been proposed as a new frontier of therapy for regulating ECM properties in the CNS. Therefore, here we aim to discuss the state of the art of MMPs and ECM abnormalities in major neuropsychiatric disorders, namely depression, bipolar disorder, and schizophrenia, the possible neuro-immune interactions involved in this complex scenario of MMPs dysregulation and propose these endopeptidases as promising targets for rational drug design.

Laminin as a Biomarker of Blood-Brain Barrier Disruption under Neuroinflammation: A Systematic Review

Laminin, a non-collagenous glycoprotein present in the brain extracellular matrix, helps to maintain blood–brain barrier (BBB) integrity and regulation. Neuroinflammation can compromise laminin structure and function, increasing BBB permeability. The aim of this paper is to determine if neuroinflammation-induced laminin functional changes may serve as a potential biomarker of alterations in the BBB. The 38 publications included evaluated neuroinflammation, BBB disruption, and laminin, and were assessed for quality and risk of bias (protocol registered in PROSPERO; CRD42020212547). We found that laminin may be a good indicator of BBB overall structural integrity, although changes in expression are dependent on the pathologic or experimental model used. In ischemic stroke, permanent vascular damage correlates with increased laminin expression (β and γ subunits), while transient damage correlates with reduced laminin expression (α subunits). Laminin was reduced in traumatic brain injury and cerebral hemorrhage studies but increased in multiple sclerosis and status epilepticus studies. Despite these observations, there is limited knowledge about the role played by different subunits or isoforms (such as 411 or 511) of laminin in maintaining structural architecture of the BBB under neuroinflammation. Further studies may clarify this aspect and the possibility of using laminin as a biomarker in different pathologies, which have alterations in BBB function in common.

Secretases Related to Amyloid Precursor Protein Processing

Alzheimer’s disease (AD) is a common neurodegenerative disease whose prevalence increases with age. An increasing number of findings suggest that abnormalities in the metabolism of amyloid precursor protein (APP), a single transmembrane aspartic protein that is cleaved by β- and γ-secretases to produce β-amyloid protein (Aβ), are a major pathological feature of AD. In recent years, a large number of studies have been conducted on the APP processing pathways and the role of secretion. This paper provides a summary of the involvement of secretases in the processing of APP and the potential drug targets that could provide new directions for AD therapy.

The dual roles of three MMPs and TIMP in innate immunity and metamorphosis in the silkworm, Bombyx mori

The matrix metalloproteinases (MMPs) and their endogenous inhibitory factors, tissue inhibitors of metalloproteinases (TIMPs), are implicated in many diseases. However, the mammalian MMPs (> 20) and TIMPs (> 3) are larger in number, and so little is known about their individual roles in organisms. Hence, we have systematically studied the roles of all three MMPs and one TIMP in silkworm innate immunity and metamorphosis. We observed that MMPs and TIMP are highly expressed during the pupation stage of the silkworms, and TIMP could interact with each MMPs. High-activity MMPs and low-activity TIMP may enhance the infection of B. mori nucleopolyhedrovirus in both in vitro and in vivo. MMPs' knockout and TIMP overexpression delayed silkworm development and even caused death. Interestingly, different MMPs' knockout led to different tubular tissue dysplasia. These findings provide insights into the conserved functions of MMPs and TIMP in human organogenesis and immunoregulation.

A Marine λ-Oligocarrageenan Inhibits Migratory and Invasive Ability of MDA-MB-231 Human Breast Cancer Cells through Actions on Heparanase Metabolism and MMP-14/MMP-2 Axis

Sugar-based molecules such as heparins or natural heparan sulfate polysaccharides have been developed and widely studied for controlling heparanase (HPSE) enzymatic activity, a key player in extracellular matrix remodelling during cancer pathogenesis. However, non-enzymatic functions of HPSE have also been described in tumour mechanisms. Given their versatile properties, we hypothesized that sugar-based inhibitors may interfere with enzymatic but also non-enzymatic HPSE activities. In this work, we assessed the effects of an original marine λ-carrageenan derived oligosaccharide (λ-CO) we previously described, along with those of its native counterpart and heparins, on cell viability, proliferation, migration, and invasion of MDA-MB-231 breast cancer cells but also of sh-MDA-MB-231 cells, in which the expression of HPSE was selectively downregulated. We observed no cytotoxic and no anti-proliferative effects of our compounds but surprisingly λ-CO was the most efficient to reduce cell migration and invasion compared with heparins, and in a HPSE-dependent manner. We provided evidence that λ-CO tightly controlled a HPSE/MMP-14/MMP-2 axis, leading to reduced MMP-2 activity. Altogether, this study highlights λ-CO as a potent HPSE “modulator” capable of reducing not only the enzymatic activity of HPSE but also the functions controlled by the HPSE levels.

The matrix metalloproteinase inhibitor IPR-179 has antiseizure and antiepileptogenic effects

Matrix metalloproteinases (MMPs) are synthesized by neurons and glia and released into the extracellular space, where they act as modulators of neuroplasticity and neuroinflammatory agents. Development of epilepsy (epileptogenesis) is associated with increased expression of MMPs, and therefore, they may represent potential therapeutic drug targets. Using quantitative PCR (qPCR) and immunohistochemistry, we studied the expression of MMPs and their endogenous inhibitors tissue inhibitors of metalloproteinases (TIMPs) in patients with status epilepticus (SE) or temporal lobe epilepsy (TLE) and in a rat TLE model. Furthermore, we tested the MMP2/9 inhibitor IPR-179 in the rapid-kindling rat model and in the intrahippocampal kainic acid mouse model. In both human and experimental epilepsy, MMP and TIMP expression were persistently dysregulated in the hippocampus compared with in controls. IPR-179 treatment reduced seizure severity in the rapid-kindling model and reduced the number of spontaneous seizures in the kainic acid model (during and up to 7 weeks after delivery) without side effects while improving cognitive behavior. Moreover, our data suggest that IPR-179 prevented an MMP2/9-dependent switch-off normally restraining network excitability during the activity period. Since increased MMP expression is a prominent hallmark of the human epileptogenic brain and the MMP inhibitor IPR-179 exhibits antiseizure and antiepileptogenic effects in rodent epilepsy models and attenuates seizure-induced cognitive decline, it deserves further investigation in clinical trials.

Serum Proteomics of Older Patients Undergoing Major Cardiac Surgery: Identification of Biomarkers Associated With Postoperative Delirium

Background

Postoperative delirium (POD) is an acute altered mental state commonly encountered after cardiac surgery. The pathophysiological mechanisms underlying POD remain unclear. We aimed to identify circulating proteins significantly altered after major cardiac surgery with cardiopulmonary bypass (CPB). We also aimed to enable inferences on associations with POD.

Methods

Serum and whole blood samples were collected before CPB (n = 16 patients; n = 8 with POD) and again from the same patients on postoperative day 1. All patients were clinically evaluated for POD on postoperative days 1–3. An aptamer-based proteomics platform (SOMAscan) was used to quantify serum protein abundance in patients with POD compared with non-POD controls. We also performed a lipopolysaccharide (LPS)-based in vitro functional analysis (TruCulture) on whole blood samples from patients with POD and non-POD controls to approximate surgical stress. Cytokine levels were determined using a Luminex immunoassay.

Results

Cardiac surgery with CPB resulted in a significant (p_adj < 0.01) change in 48.8% (637 out of 1,305) of proteins detected by SOMAscan. Gene set enrichment showed that the most impacted biological processes involved myeloid cell activation. Specifically, activation and degranulation of neutrophils were the top five highest-scoring processes. Pathway analyses with the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that metabolic enzymes, particularly those of glycolysis, were elevated in serum concentration after surgery. Several proteins were significantly increased postoperatively in patients diagnosed with POD relative to the non-POD controls, with interleukin-6 (IL-6) showing the greatest fold-change. LPS stimulation of whole blood samples confirmed these findings. Linear regression analysis showed a highly significant correlation between Confusion Assessment Method (CAM) scores and CPB-mediated changes in cGMP-inhibited 3′,5′-cyclic phosphodiesterase A (PDE3A).

Conclusions

Cardiac surgery with CPB resulted in inflammasome changes accompanied by unexpected increases in metabolic pathways. In exploratory analyses, we found that POD was associated with changes in the expression level of various proteins, most notably IL-6 and PDE3A. This study and ongoing protein biomarker studies will likely help quantify risk or confirm the diagnosis for POD and increase understanding of its pathophysiological mechanisms.

Serum Proteomics of Older Patients Undergoing Major Cardiac Surgery: Identification of Biomarkers Associated With Postoperative Delirium

BACKGROUND

Postoperative delirium (POD) is an acute altered mental state commonly encountered after cardiac surgery. The pathophysiological mechanisms underlying POD remain unclear. We aimed to identify circulating proteins significantly altered after major cardiac surgery with cardiopulmonary bypass (CPB). We also aimed to enable inferences on associations with POD.

METHODS

Serum and whole blood samples were collected before CPB (n = 16 patients; n = 8 with POD) and again from the same patients on postoperative day 1. All patients were clinically evaluated for POD on postoperative days 1-3. An aptamer-based proteomics platform (SOMAscan) was used to quantify serum protein abundance in patients with POD compared with non-POD controls. We also performed a lipopolysaccharide (LPS)-based in vitro functional analysis (TruCulture) on whole blood samples from patients with POD and non-POD controls to approximate surgical stress. Cytokine levels were determined using a Luminex immunoassay.

RESULTS

Cardiac surgery with CPB resulted in a significant (p_adj < 0.01) change in 48.8% (637 out of 1,305) of proteins detected by SOMAscan. Gene set enrichment showed that the most impacted biological processes involved myeloid cell activation. Specifically, activation and degranulation of neutrophils were the top five highest-scoring processes. Pathway analyses with the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that metabolic enzymes, particularly those of glycolysis, were elevated in serum concentration after surgery. Several proteins were significantly increased postoperatively in patients diagnosed with POD relative to the non-POD controls, with interleukin-6 (IL-6) showing the greatest fold-change. LPS stimulation of whole blood samples confirmed these findings. Linear regression analysis showed a highly significant correlation between Confusion Assessment Method (CAM) scores and CPB-mediated changes in cGMP-inhibited 3',5'-cyclic phosphodiesterase A (PDE3A).

CONCLUSIONS

Cardiac surgery with CPB resulted in inflammasome changes accompanied by unexpected increases in metabolic pathways. In exploratory analyses, we found that POD was associated with changes in the expression level of various proteins, most notably IL-6 and PDE3A. This study and ongoing protein biomarker studies will likely help quantify risk or confirm the diagnosis for POD and increase understanding of its pathophysiological mechanisms.

MT5-MMP controls APP and β-CTF/C99 metabolism through proteolytic-dependent and -independent mechanisms relevant for Alzheimer's disease

We previously discovered the implication of membrane-type 5-matrix metalloproteinase (MT5-MMP) in Alzheimer's disease (AD) pathogenesis. Here, we shed new light on pathogenic mechanisms by which MT5-MMP controls the processing of amyloid precursor protein (APP) and the fate of amyloid beta peptide (Aβ) as well as its precursor C99, and C83. We found in human embryonic kidney cells (HEK) carrying the APP Swedish familial mutation (HEKswe) that deleting the C-terminal non-catalytic domains of MT5-MMP hampered its ability to process APP and release the soluble 95 kDa form (sAPP95). Catalytically inactive MT5-MMP variants increased the levels of Aβ and promoted APP/C99 sorting in the endolysosomal system, likely through interactions of the proteinase C-terminal portion with C99. Most interestingly, the deletion of the C-terminal domain of MT5-MMP caused a strong degradation of C99 by the proteasome and prevented Aβ accumulation. These discoveries reveal new control of MT5-MMP over APP by proteolytic and non-proteolytic mechanisms driven by the C-terminal domains of the proteinase. The targeting of these non-catalytic domains of MT5-MMP could, therefore, provide new insights into the therapeutic regulation of APP-related pathology in AD.

Repetitive transcranial magnetic stimulation activates glial cells and inhibits neurogenesis after pneumococcal meningitis

Pneumococcal meningitis (PM) causes damage to the hippocampus, a brain structure critically involved in learning and memory. Hippocampal injury-which compromises neurofunctional outcome-occurs as apoptosis of progenitor cells and immature neurons of the hippocampal dentate granule cell layer thereby impairing the regenerative capacity of the hippocampal stem cell niche. Repetitive transcranial magnetic stimulation (rTMS) harbours the potential to modulate the proliferative activity of this neuronal stem cell niche. In this study, specific rTMS protocols-namely continuous and intermittent theta burst stimulation (cTBS and iTBS)-were applied on infant rats microbiologically cured from PM by five days of antibiotic treatment. Following two days of exposure to TBS, differential gene expression was analysed by whole transcriptome analysis using RNAseq. cTBS provoked a prominent effect in inducing differential gene expression in the cortex and the hippocampus, whereas iTBS only affect gene expression in the cortex. TBS induced polarisation of microglia and astrocytes towards an inflammatory phenotype, while reducing neurogenesis, neuroplasticity and regeneration. cTBS was further found to induce the release of pro-inflammatory cytokines in vitro. We conclude that cTBS intensified neuroinflammation after PM, which translated into increased release of pro-inflammatory mediators thereby inhibiting neuroregeneration.

Combined therapy with ceftriaxone and doxycycline does not improve the outcome of meningococcal meningitis in mice compared to ceftriaxone monotherapy

BACKGROUND

Meningococcal meningitis (MM) is a life-threatening disease associated with approximately 10% case fatality rates and neurological sequelae in 10-20% of the cases. Recently, we have shown that the matrix metalloproteinase (MMP) inhibitor BB-94 reduced brain injury in a mouse model of MM. The present study aimed to assess whether doxycycline (DOX), a tetracycline that showed a neuroprotective effect as adjuvant therapy in experimental pneumococcal meningitis (PM), would also exert a beneficial effect when given as adjunctive therapy to ceftriaxone (CRO) in experimental MM.

METHODS

BALB/c mice were infected by the intracisternal route with a group C Neisseria meningitidis strain. Eighteen h post infection (hpi), animals were randomised for treatment with CRO [100 mg/kg subcutaneously (s.c.)], CRO plus DOX (30 mg/kg s.c.) or saline (control s.c.). Antibiotic treatment was repeated 24 and 40 hpi. Mouse survival and clinical signs, bacterial counts in cerebella, brain damage, MMP-9 and cyto/chemokine levels were assessed 48 hpi.

RESULTS

Analysis of bacterial load in cerebella indicated that CRO and CRO + DOX were equally effective at controlling meningococcal replication. No differences in survival were observed between mice treated with CRO (94.4%) or CRO + DOX (95.5%), (p > 0.05). Treatment with CRO + DOX significantly diminished both the number of cerebral hemorrhages (p = 0.029) and the amount of MMP-9 in the brain (p = 0.046) compared to untreated controls, but not to CRO-treated animals (p > 0.05). Levels of inflammatory markers in the brain of mice that received CRO or CRO + DOX were not significantly different (p > 0.05). Overall, there were no significant differences in the parameters assessed between the groups treated with CRO alone or CRO + DOX.

CONCLUSIONS

Treatment with CRO + DOX showed similar bactericidal activity to CRO in vivo, suggesting no antagonist effect of DOX on CRO. Combined therapy significantly improved mouse survival and disease severity compared to untreated animals, but addition of DOX to CRO did not offer significant benefits over CRO monotherapy. In contrast to experimental PM, DOX has no adjunctive activity in experimental MM.

Matrix Metalloproteinases as New Targets in Alzheimer's Disease: Opportunities and Challenges

Although matrix metalloproteinases (MMPs) are implicated in the regulation of numerous physiological processes, evidence of their pathological roles have also been obtained in the last decades, making MMPs attractive therapeutic targets for several diseases. Recent discoveries of their involvement in central nervous system (CNS) disorders, and in particular in Alzheimer's disease (AD), have paved the way to consider MMP modulators as promising therapeutic strategies. Over the past few decades, diverse approaches have been undertaken in the design of therapeutic agents targeting MMPs for various purposes, leading, more recently, to encouraging developments. In this article, we will present recent examples of inhibitors ranging from small molecules and peptidomimetics to biologics. We will also discuss the scientific knowledge that has led to the development of emerging tools and techniques to overcome the challenges of selective MMP inhibition.

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.

Nerve, Muscle, and Synaptogenesis

The vertebrate skeletal neuromuscular junction (NMJ) has long served as a model system for studying synapse structure, function, and development. Over the last several decades, a neuron-specific isoform of agrin, a heparan sulfate proteoglycan, has been identified as playing a central role in synapse formation at all vertebrate skeletal neuromuscular synapses. While agrin was initially postulated to be the inductive molecule that initiates synaptogenesis, this model has been modified in response to work showing that postsynaptic differentiation can develop in the absence of innervation, and that synapses can form in transgenic mice in which the agrin gene is ablated. In place of a unitary mechanism for neuromuscular synapse formation, studies in both mice and zebrafish have led to the proposal that two mechanisms mediate synaptogenesis, with some synapses being induced by nerve contact while others involve the incorporation of prepatterned postsynaptic structures. Moreover, the current model also proposes that agrin can serve two functions, to induce synaptogenesis and to stabilize new synapses, once these are formed. This review examines the evidence for these propositions, and concludes that it remains possible that a single molecular mechanism mediates synaptogenesis at all NMJs, and that agrin acts as a stabilizer, while its role as inducer is open to question. Moreover, if agrin does not act to initiate synaptogenesis, it follows that as yet uncharacterized molecular interactions are required to play this essential inductive role. Several alternatives to agrin for this function are suggested, including focal pericellular proteolysis and integrin signaling, but all require experimental validation.

Emerging Alternative Proteinases in APP Metabolism and Alzheimer's Disease Pathogenesis: A Focus on MT1-MMP and MT5-MMP

Processing of amyloid beta precursor protein (APP) into amyloid-beta peptide (Aβ) by β-secretase and γ-secretase complex is at the heart of the pathogenesis of Alzheimer’s disease (AD). Targeting this proteolytic pathway effectively reduces/prevents pathology and cognitive decline in preclinical experimental models of the disease, but therapeutic strategies based on secretase activity modifying drugs have so far failed in clinical trials. Although this may raise some doubts on the relevance of β- and γ-secretases as targets, new APP-cleaving enzymes, including meprin-β, legumain (δ-secretase), rhomboid-like protein-4 (RHBDL4), caspases and membrane-type matrix metalloproteinases (MT-MMPs/η-secretases) have confirmed that APP processing remains a solid mechanism in AD pathophysiology. This review will discuss recent findings on the roles of all these proteinases in the nervous system, and in particular on the roles of MT-MMPs, which are at the crossroads of pathological events involving not only amyloidogenesis, but also inflammation and synaptic dysfunctions. Assessing the potential of these emerging proteinases in the Alzheimer’s field opens up new research prospects to improve our knowledge of fundamental mechanisms of the disease and help us establish new therapeutic strategies.

Understanding the complexity of the matrix metalloproteinase system and its relevance to age-related diseases: Age-related macular degeneration and Alzheimer's disease

Extracellular matrices (ECMs) are maintained by tightly coupled processes of continuous synthesis and degradation. The degradative arm is mediated by a family of proteolytic enzymes called the matrix metalloproteinases (MMPs). These enzymes are released as latent proteins (pro-MMPs) and on activation are capable of degrading most components of an ECM. Activity of these enzymes is checked by the presence of tissue inhibitors of MMPs (TIMPs) and current opinion holds that the ratio of TIMPs/MMPs determines the relative rate of degradation. Thus, elevated ratios are thought to compromise degradation leading to the accumulation of abnormal ECM material, whilst diminished ratios are thought to lead to excessive ECM degradation (facilitating angiogenesis and the spread of cancer cells). Our recent work has shown this system to be far more complex. MMP species tend to undergo covalent modification leading to homo- and hetero-dimerization and aggregation resulting in the formation of very large macromolecular weight MMP complexes (LMMCs). In addition, the various MMP species also show a bound-free compartmentalisation. The net result of these changes is to reduce the availability of the latent forms of MMPs for the activation process. An assessment of the degradation potential of the MMP system in any tissue must therefore take into account the degree of sequestration of the latent MMP species, a protocol that has not previously been addressed. Taking into consideration the complexities already described, we will present an analysis of the MMP system in two common neurodegenerative disorders, namely age-related macular degeneration (AMD) and Alzheimer's disease (AD).

Metalloproteinases and their tissue inhibitors in Alzheimer's disease and other neurodegenerative disorders

As life expectancy increases worldwide, age-related neurodegenerative diseases will increase in parallel. The lack of effective treatment strategies may soon lead to an unprecedented health, social and economic crisis. Any attempt to halt the progression of these diseases requires a thorough knowledge of the pathophysiological mechanisms involved to facilitate the identification of new targets and the application of innovative therapeutic strategies. The metzincin superfamily of metalloproteinases includes matrix metalloproteinases (MMP), a disintegrin and metalloproteinase (ADAM) and ADAM with thrombospondin motifs (ADAMTS). These multigenic and multifunctional proteinase families regulate the functions of an increasing number of signalling and scaffolding molecules involved in neuroinflammation, blood-brain barrier disruption, protein misfolding, synaptic dysfunction or neuronal death. Metalloproteinases and their physiological inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), are therefore, at the crossroads of molecular and cellular mechanisms that support neurodegenerative processes, and emerge as potential new therapeutic targets. We provide an overview of current knowledge on the role and regulation of metalloproteinases and TIMPs in four major neurodegenerative diseases: Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease.

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.

Demystifying the extracellular matrix and its proteolytic remodeling in the brain: structural and functional insights

The extracellular matrix (ECM) plays diverse roles in several physiological and pathological conditions. In the brain, the ECM is unique both in its composition and in functions. Furthermore, almost all the cells in the central nervous system contribute to different aspects of this intricate structure. Brain ECM, enriched with proteoglycans and other small proteins, aggregate into distinct structures around neurons and oligodendrocytes. These special structures have cardinal functions in the normal functioning of the brain, such as learning, memory, and synapse regulation. In this review, we have compiled the current knowledge about the structure and function of important ECM molecules in the brain and their proteolytic remodeling by matrix metalloproteinases and other enzymes, highlighting the special structures they form. In particular, the proteoglycans in brain ECM, which are essential for several vital functions, are emphasized in detail.

Cerebellum Susceptibility to Neonatal Asphyxia: Possible Protective Effects of N-Acetylcysteine Amide

Background

After perinatal asphyxia, the cerebellum presents more damage than previously suggested.

Objectives

To explore if the antioxidant N-acetylcysteine amide (NACA) could reduce cerebellar injury after hypoxia-reoxygenation in a neonatal pig model.

Methods

Twenty-four newborn pigs in two intervention groups were exposed to 8% oxygen and hypercapnia, until base excess fell to -20 mmol/l or the mean arterial blood pressure declined to <20 mmHg. After hypoxia, they received either NACA (NACA group, n = 12) or saline (vehicle-treated group, n = 12). One sham-operated group (n = 5) served as a control and was not subjected to hypoxia. Observation time after the end of hypoxia was 9.5 hours.

Results

The intranuclear proteolytic activity in Purkinje cells of asphyxiated vehicle-treated pigs was significantly higher than that in sham controls (p = 0.03). Treatment with NACA was associated with a trend to decreased intranuclear proteolytic activity (p = 0.08), There were significantly less mutations in the mtDNA of the NACA group compared with the vehicle-treated group, 2.0 × 10^-4 (±2.0 × 10^-4) versus 4.8 × 10^-5(±3.6 × 10^-4, p < 0.05).

Conclusion

We found a trend to lower proteolytic activity in the core of Purkinje cells and significantly reduced mutation rate of mtDNA in the NACA group, which may indicate a positive effect of NACA after neonatal hypoxia. Measuring the proteolytic activity in the nucleus of Purkinje cells could be used to assess the effect of different neuroprotective substances after perinatal asphyxia.

Discovery of a highly selective chemical inhibitor of matrix metalloproteinase-9 (MMP-9) that allosterically inhibits zymogen activation

Aberrant activation of matrix metalloproteinases (MMPs) is a common feature of pathological cascades observed in diverse disorders, such as cancer, fibrosis, immune dysregulation, and neurodegenerative diseases. MMP-9, in particular, is highly dynamically regulated in several pathological processes. Development of MMP inhibitors has therefore been an attractive strategy for therapeutic intervention. However, a long history of failed clinical trials has demonstrated that broad-spectrum MMP inhibitors have limited clinical utility, which has spurred the development of inhibitors selective for individual MMPs. Attaining selectivity has been technically challenging because of sequence and structural conservation across the various MMPs. Here, through a biochemical and structural screening paradigm, we have identified JNJ0966, a highly selective compound that inhibited activation of MMP-9 zymogen and subsequent generation of catalytically active enzyme. JNJ0966 had no effect on MMP-1, MMP-2, MMP-3, MMP-9, or MMP-14 catalytic activity and did not inhibit activation of the highly related MMP-2 zymogen. The molecular basis for this activity was characterized as an interaction of JNJ0966 with a structural pocket in proximity to the MMP-9 zymogen cleavage site near Arg-106, which is distinct from the catalytic domain. JNJ0966 was efficacious in reducing disease severity in a mouse experimental autoimmune encephalomyelitis model, demonstrating the viability of this therapeutic approach. This discovery reveals an unprecedented pharmacological approach to MMP inhibition, providing an opportunity to improve selectivity of future clinical drug candidates. Targeting zymogen activation in this manner may also allow for pharmaceutical exploration of other enzymes previously viewed as intractable drug targets.

Detection of Matrix Metalloproteinases by Zymography

Matrix metalloproteinases (MMPs) represent more than 20 zinc-containing endopeptidases that cleave internal peptide bonds, leading to protein degradation. They play a critical role in many physiological cell functions, including tissue remodeling, embryogenesis, and angiogenesis. They are also involved in the pathogenesis of a vast array of diseases, including but not limited to systemic inflammation, various cancers, and cardiovascular, neurological, and autoimmune diseases. Here, we describe gel zymography to detect MMPs in cell and tissue samples and in cell culture supernatants.

Adipocyte-secreted chemerin is processed to a variety of isoforms and influences MMP3 and chemokine secretion through an NFkB-dependent mechanism

Obesity is associated with white adipose tissue (WAT) remodelling characterized by changes in cellular composition, size, and adipokine secretion. Levels of the adipokine chemerin are positively associated with obesity; however, the biological function of chemerin in WAT is poorly understood. We identified factors involved in WAT remodelling, including matrix metalloproteinase (Mmp)3 and chemokines (Ccl2, 3, 5, 7), as novel targets of chemerin signalling in mature adipocytes. Inhibition of chemerin signalling increased MMP activity and the recruitment of macrophages towards adipocyte-conditioned media. These effects were mediated through increases in NFkB signalling, suggesting that chemerin exerts an anti-inflammatory influence. We also demonstrate that multiple chemerin isoforms are present in adipocyte-conditioned media and that adipocyte-secreted chemerin, but not synthetic chemerin, recapitulates the activity of endogenous chemerin. Considered altogether, this suggests that endogenously secreted chemerin plays an autocrine/paracrine role in WAT, identifying chemerin as a therapeutic target to modulate adipose remodelling.

Gene expression comparison reveals distinct basal expression of HOX members and differential TNF-induced response between brain- and spinal cord-derived microvascular endothelial cells

Background

The heterogeneity of endothelial cell types underlies their remarkable ability to sub-specialize and provide specific requirements for a given vascular bed. Here, we compared rat microvascular endothelial cells (MECs) derived from the brain and spinal cord in both basal and inflammatory conditions.

Methods

We used whole rat genome microarrays to compare, at different time points, basal and TNF-α-induced gene expression of rat MECs from in vitro models of the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB). Validation at both messenger RNA (mRNA) and protein levels was performed on freshly extracted microvessels (MVs) from the brain and spinal cord (BMVs and SCMVs, respectively), as these were considered the closest in vivo tissues to cultured MECs.

Results

Most of the genes encoding adhesion/tight junction molecules and known endothelial markers were similarly expressed in brain and spinal cord MECs (BMECs and SCMECs, respectively). However, one striking finding was the higher expression of several Hox genes, which encode transcription factors involved in positional identity. The differential expression of Hoxa9 and Hoxb7 at the mRNA levels as well as protein levels was confirmed in BMVs and SCMVs. Although the TNF-α response was in general higher in BMECs than in SCMECs at 12 h, the opposite was observed at 48 h. Furthermore, we found that expression of Tnfrsf1a and Tnfrsf1b encoding the TNF receptor super-family member 1a/TNFR1 and 1b/TNFR2, respectively, were constitutively higher in BMVs compared to SCMVs. However, only Tnfrsf1b was induced in SCMECs in response to TNF-α at 24 and 48 h.

Conclusions

Our results support a role for HOX members in defining the positional identities of MECs in vivo. Our data also suggest that the delayed transcriptional activation upon TNF-α treatment in SCMECs results from the requirement of the TNF-induced expression of Tnfrsf1b. In contrast, its high basal expression in BMECs might be sufficient to confer an immediate and efficient TNF-α response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0749-6) contains supplementary material, which is available to authorized users.

MT5-MMP, just a new APP processing proteinase in Alzheimer's disease?

We have recently identified in a transgenic mouse model of Alzheimer’s disease (AD) membrane-type 5-MMP (MT5-MMP) as a new player in Alzheimer’s pathogenesis, which displays pro-amyloidogenic features and proteolytic processing of amyloid precursor protein (APP). Another group has reported that MT5-MMP processing of APP may release a novel neurotoxic APP fragment. Although MT5-MMP-mediated APP processing appears to be a key pathogenic step, we hypothesize that MT5-MMP may also contribute to AD pathogenesis through complementary mechanisms that involve the activation of pro-inflammatory pathways and/or APP trafficking.

Abnormal activation of calpain and protein kinase Cα promotes a constitutive release of matrix metalloproteinase 9 in peripheral blood mononuclear cells from cystic fibrosis patients

Matrix metalloproteinase 9 (MMP9) is physiologically involved in remodeling the extracellular matrix components but its abnormal release has been observed in several human pathologies. We here report that peripheral blood mononuclear cells (PBMCs), isolated from cystic fibrosis (CF) patients homozygous for F508del-cystic fibrosis transmembrane conductance regulator (CFTR), express constitutively and release at high rate MMP9 due to the alteration in their intracellular Ca(2+) homeostasis. This spontaneous and sustained MMP9 secretion may contribute to the accumulation of this protease in fluids of CF patients. Conversely, in PBMCs isolated from healthy donors, expression and secretion of MMP9 are undetectable but can be evoked, after 12 h of culture, by paracrine stimulation which also promotes an increase in [Ca(2+)]i. We also demonstrate that in both CF and control PBMCs the Ca(2+)-dependent MMP9 secretion is mediated by the concomitant activation of calpain and protein kinase Cα (PKCα), and that MMP9 expression involves extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) phosphorylation. Our results are supported by the fact that either the inhibition of Ca(2+) entry or chelation of [Ca(2+)]i as well as the inhibition of single components of the signaling pathway or the restoration of CFTR activity all promote the reduction of MMP9 secretion.

Surgery-Induced Hippocampal Angiotensin II Elevation Causes Blood-Brain Barrier Disruption via MMP/TIMP in Aged Rats

Reversible blood-brain barrier (BBB) disruption has been uniformly reported in several animal models of postoperative cognitive dysfunction (POCD). Nevertheless, the precise mechanism underlying this occurrence remains unclear. Using an aged rat model of POCD, we investigated the dynamic changes in expression of molecules involved in BBB disintegration, matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9), as well as three of their endogenous tissue inhibitors of MMP (TIMP-1, -2, -3), and tried to establish the correlation between MMP/TIMP balance and surgery-induced hippocampal BBB disruption. We validated the increased hippocampal expression of angiotensin II (Ang II) and Ang II receptor type 1 (AT1) after surgery. We also found MMP/TIMP imbalance as early as 6 h after surgery, together with increased BBB permeability and decreased expression of Occludin and zonula occludens-1 (ZO-1), as well as increased basal lamina protein laminin at 24 h postsurgery. The AT1 antagonist candesartan restored MMP/TIMP equilibrium and modulated expression of Occludin and laminin, but not ZO-1, thereby improving BBB permeability. These events were accompanied by suppression of the surgery-induced canonical nuclear factor-κB (NF-κB) activation cascade. Nevertheless, AT1 antagonism did not affect nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) expression. Collectively, these findings suggest that surgery-induced Ang II release impairs BBB integrity by activating NF-κB signaling and disrupting downstream MMP/TIMP balance via AT1 receptor.

MT5-MMP is a new pro-amyloidogenic proteinase that promotes amyloid pathology and cognitive decline in a transgenic mouse model of Alzheimer's disease

Membrane-type 5-matrix metalloproteinase (MT5-MMP) is a proteinase mainly expressed in the nervous system with emerging roles in brain pathophysiology. The implication of MT5-MMP in Alzheimer's disease (AD), notably its interplay with the amyloidogenic process, remains elusive. Accordingly, we crossed the genetically engineered 5xFAD mouse model of AD with MT5-MMP-deficient mice and examined the impact of MT5-MMP deficiency in bigenic 5xFAD/MT5-MMP(-/-) mice. At early stages (4 months) of the pathology, the levels of amyloid beta peptide (Aβ) and its amyloid precursor protein (APP) C-terminal fragment C99 were largely reduced in the cortex and hippocampus of 5xFAD/MT5-MMP(-/-), compared to 5xFAD mice. Reduced amyloidosis in bigenic mice was concomitant with decreased glial reactivity and interleukin-1β (IL-1β) levels, and the preservation of long-term potentiation (LTP) and spatial learning, without changes in the activity of α-, β- and γ-secretases. The positive impact of MT5-MMP deficiency was still noticeable at 16 months of age, as illustrated by reduced amyloid burden and gliosis, and a better preservation of the cortical neuronal network and synaptophysin levels in bigenic mice. MT5-MMP expressed in HEKswe cells colocalized and co-immunoprecipitated with APP and significantly increased the levels of Aβ and C99. MT5-MMP also promoted the release of a soluble APP fragment of 95 kDa (sAPP95) in HEKswe cells. sAPP95 levels were significantly reduced in brain homogenates of 5xFAD/MT5-MMP(-/-) mice, supporting altogether the idea that MT5-MMP influences APP processing. MT5-MMP emerges as a new pro-amyloidogenic regulator of APP metabolism, whose deficiency alleviates amyloid pathology, neuroinflammation and cognitive decline.

Bacterial meningitis: insights into pathogenesis and evaluation of new treatment options: a perspective from experimental studies

Bacterial meningitis is associated with high mortality and morbidity rates. Bacterial components induce an overshooting inflammatory reaction, eventually leading to brain damage. Pathological correlates of neurofunctional deficits include cortical necrosis, damage of the inner ear and hippocampal apoptosis. The hippocampal dentate gyrus is important for memory acquisition and harbors a neuronal stem cell niche, thus being potentially well equipped for regeneration. Adjuvant therapies aimed at decreasing the inflammatory reaction, for example, dexamethasone, and those protecting the brain from injury have been evaluated in animal models of the disease. They include nonbacteriolytic antibiotics (e.g., daptomycin), metalloproteinase inhibitors and modulators of the immunological response, for example, granulocyte colony-stimulating factor. Increasing research interest has recently been focused on interventions aimed at supporting regenerative processes.

The matrix metalloproteinase inhibitor RS-130830 attenuates brain injury in experimental pneumococcal meningitis

Background

Pneumococcal meningitis (PM) is characterized by high mortality and morbidity including long-term neurofunctional deficits. Neuropathological correlates of these sequelae are apoptosis in the hippocampal dentate gyrus and necrosis in the cortex. Matrix metalloproteinases (MMPs) play a critical role in the pathophysiology of PM. RS-130830 (Ro-1130830, CTS-1027) is a potent partially selective inhibitor of MMPs of a second generation and has been evaluated in clinical trials as an anti-arthritis drug. It inhibits MMPs involved in acute inflammation but has low activity against MMP-1 (interstitial collagenase), MMP-7 (matrilysin) and tumour necrosis factor α converting enzyme (TACE).

Methods

A well-established infant rat model of PM was used where live Streptococcus pneumoniae were injected intracisternally and antibiotic treatment with ceftriaxone was initiated 18 h post infection (hpi). Treatment with RS-130830 (75 mg/kg bis in die (bid) i.p., n = 40) was started at 3 hpi while control littermates received the vehicle (succinylated gelatine, n = 42).

Results

Cortical necrosis was significantly attenuated in animals treated with RS-130830, while the extent of hippocampal apoptosis was not influenced. At 18 hpi, concentrations of interleukin (IL)-1β and IL-10 were significantly lower in the cerebrospinal fluid of treated animals compared to controls. RS-130830 significantly reduced weight loss and leukocyte counts in the cerebrospinal fluid of survivors of PM.

Conclusion

This study identifies MMP inhibition, specifically with RS-130830, as an efficient strategy to attenuate disease severity and cortical brain injury in PM.