Impact of the matrix metalloproteinase MMP-3 on dementia

Impact of MMP2 rs243865 and MMP3 rs3025058 Polymorphisms on Clinical Findings in Alzheimer's Disease Patients

Alzheimer's disease (AD) is a chronic neurodegenerative disease of the central nervous system with higher prevalence in elderly people. Despite numerous research studies, the etiopathogenesis of AD remains unclear. Matrix metalloproteinases (MMPs) are endopeptidases involved in the cleavage of extracellular matrix proteins and basement membrane compounds. In the brain, the pathological role of MMPs includes the disruption of the blood-brain barrier leading to the induction of neuroinflammation. Among various MMPs, MMP-2 and MMP-3 belong to candidate molecules related to AD pathology. In our study, we aimed to evaluate the association of MMP2 rs243865 and MMP3 rs3025058 polymorphisms with AD susceptibility and their influence on age at onset and MoCA score in patients from Slovakia. Both MMP gene promoter polymorphisms were genotyped in 171 AD patients and 308 controls by the PCR-RFLP method. No statistically significant differences in the distribution of MMP2 rs243865 (-1306 C>T) and MMP3 rs3025058 (-1171 5A>6A) alleles/genotypes were found between AD patients and the control group. However, correlation with clinical findings revealed later age at disease onset in MMP2 rs243865 CC carriers in the dominant model as compared to T allele carriers (CC vs. CT+TT: 78.44 ± 6.28 vs. 76.36 ± 6.39, p = 0.036). The results of MMP3 rs3025058 analysis revealed that 5A/6A carriers in the overdominant model tended to have earlier age at disease onset as compared to other MMP3 genotype carriers (5A/6A vs. 5A/5A+6A/6A: 76.61 ± 5.88 vs. 78.57 ± 6.79, p = 0.045). In conclusion, our results suggest that MMP2 rs243865 and MMP3 rs3025058 promoter polymorphisms may have influence on age at onset in AD patients.

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

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

Association between perinatal methylation of the neuronal differentiation regulator HES1 and later childhood neurocognitive function and behaviour

Background Early life environments induce long-term changes in neurocognitive development and behaviour. In animal models, early environmental cues affect neuropsychological phenotypes via epigenetic processes but, as yet, there is little direct evidence for such mechanisms in humans.

Method We examined the relation between DNA methylation at birth and child neuropsychological outcomes in two culturally diverse populations using a genome-wide methylation analysis and validation by pyrosequencing.

Results Within the UK Southampton Women’s Survey (SWS) we first identified 41 differentially methylated regions of interest (DMROI) at birth associated with child’s full-scale IQ at age 4 years. Associations between HES1 DMROI methylation and later cognitive function were confirmed by pyrosequencing in 175 SWS children. Consistent with these findings, higher HES1 methylation was associated with higher executive memory function in a second independent group of 200 SWS 7-year-olds. Finally, we examined a pathway for this relationship within a Singaporean cohort (n = 108). Here, HES1 DMROI methylation predicted differences in early infant behaviour, known to be associated with academic success. In vitro, methylation of HES1 inhibited ETS transcription factor binding, suggesting a functional role of this site.

Conclusions Thus, our findings suggest that perinatal epigenetic processes mark later neurocognitive function and behaviour, providing support for a role of epigenetic processes in mediating the long-term consequences of early life environment on cognitive development.

Matrix metalloproteinases and their multiple roles in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent type of dementia. Pathological changes in the AD brain include amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs), as well as neuronal death and synaptic loss. Matrix metalloproteinases (MMPs) play an important role as inflammatory components in the pathogenesis of AD. MMP-2 might be assumed to have a protective role in AD and is the major MMP which is directly linked to Aβ in the brain. Synthesis of MMP-9 can be induced by Aβ, and the enzymes appear to exert multiple effects in AD in senile plaque homoeostasis. The proaggregatory influence on tau oligomer formation in strategic brain regions may be a potential neurotoxic side effect of MMP-9. MMP-3 levels are correlated to the duration of AD and correlate with the CSF T-tau and P-tau levels in the elderly controls. Elevated brain levels of MMP-3 might result in increased MMP-9 activity and indirectly facilitate tau aggregation. At present, the clinical utility of these proteins, particularly in plasma or serum, as potential early diagnostic biomarkers for AD remains to be established. More research is needed to understand the diverse roles of these proteases to design specific drugs and devise therapeutic strategies for AD.

The role of Beta-adrenergic receptor blockers in Alzheimer's disease: potential genetic and cellular signaling mechanisms

According to genetic studies, Alzheimer's disease (AD) is linked to beta-adrenergic receptor blockade through numerous factors, including human leukocyte antigen genes, the renin-angiotensin system, poly(adenosine diphosphate-ribose) polymerase 1, nerve growth factor, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate. Beta-adrenergic receptor blockade is also implicated in AD due to its effects on matrix metalloproteinases, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, and nitric oxide synthase. Beta-adrenergic receptor blockade may also have a significant role in AD, although the role is controversial. Behavioral symptoms, sex, or genetic factors, including Beta 2-adrenergic receptor variants, apolipoprotein E, and cytochrome P450 CYP2D6, may contribute to beta-adrenergic receptor blockade modulation in AD. Thus, the characterization of beta-adrenergic receptor blockade in patients with AD is needed.

The role of vitamin D in Alzheimer's disease: possible genetic and cell signaling mechanisms

Alzheimer's disease (AD) is the most common form of dementia in the elderly individuals and is associated with progressive memory loss and cognitive dysfunction. A significant association between AD and low levels of vitamin D has been demonstrated. Furthermore, vitamin D supplements appear to have a beneficial clinical effect on AD by regulating micro-RNA, enhancing toll-like receptors, modulating vascular endothelial factor expression, modulating angiogenin, and advanced glycation end products. Vitamin D also exerts its effects on AD by regulating calcium-sensing receptor expression, enhancing amyloid-β peptides clearance, interleukin 10, downregulating matrix metalloproteinases, upregulating heme oxygenase 1, and suppressing the reduced form of nicotinamide adenine dinucleotide phosphate expression. In conclusion, vitamin D may play a beneficial role in AD. Calcitriol is the best vitamin D supplement for AD, because it is the active form of the vitamin D3 metabolite and modulates inflammatory cytokine expression. Therefore, further investigation of the role of calcitriol in AD is needed.

Are amyloid-degrading enzymes viable therapeutic targets in Alzheimer's disease?

: The amyloid cascade hypothesis of Alzheimer's disease envisages that the initial elevation of amyloid β-peptide (Aβ) levels, especially of Aβ(1-42) , is the primary trigger for the neuronal cell death specific to onset of Alzheimer's disease. There is now substantial evidence that brain amyloid levels are manipulable because of a dynamic equilibrium between their synthesis from the amyloid precursor protein and their removal by amyloid-degrading enzymes (ADEs) providing a potential therapeutic strategy. Since the initial reports over a decade ago that two zinc metallopeptidases, insulin-degrading enzyme and neprilysin (NEP), contributed to amyloid degradation in the brain, there is now an embarras de richesses in relation to this category of enzymes, which currently number almost 20. These now include serine and cysteine proteinases, as well as numerous zinc peptidases. The experimental validation for each of these enzymes, and which to target, varies enormously but up-regulation of several of them individually in mouse models of Alzheimer's disease has proved effective in amyloid and plaque clearance, as well as cognitive enhancement. The relative status of each of these enzymes will be critically evaluated. NEP and its homologues, as well as insulin-degrading enzyme, remain as principal ADEs and recently discovered mechanisms of epigenetic regulation of NEP expression potentially open new avenues in manipulation of AD-related genes, including ADEs.

Role of matrix metalloproteinase-3 in neurodegeneration

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

Matrix metalloproteinases in peripheral blood and cerebrospinal fluid in patients with Alzheimer's disease

BACKGROUND

Deposition of amyloid beta in senile plaques and in cerebral blood vessels is one hallmark of the pathogenesis of Alzheimer's disease (AD). The ability of several matrix metalloproteinases (MMPs) to degrade amyloid precursor protein leading to aggregation of amyloid beta, as well as the increased expression of MMPs in post mortem brain tissue of Alzheimer's patients, indicate that MMPs play an important role in the pathogenesis of AD.

METHODS

We investigated levels of MMP-2,-3,-9 and -10 in plasma and cerebrospinal fluid (CSF) of AD patients (n = 14) by gelatin and casein zymography. Comparisons between AD patients and controls relative to levels of MMP-2, MMP-3, MMP-9, and MMP-10 were made with Wilcoxon rank statistics. Pearson correlations were computed as measures of association.

RESULTS

MMP-3 in AD was significantly elevated in plasma (p = 0.006) and there was a trend towards increase in CSF (p = 0.05). MMP-2 in CSF of AD patients was significantly decreased (p = 0.02) while levels in plasma remained unchanged. MMP-9 and MMP-10 could not be detected in CSF; MMP-10 was unchanged in plasma, but MMP-9 was significantly decreased (p = 0.02).

CONCLUSIONS

These findings constitute further evidence for the important role of MMPs in the pathogenesis of AD.

Alterations of matrix metalloproteinases in the healthy elderly with increased risk of prodromal Alzheimer's disease

Introduction

Matrix metalloproteinases (MMP) are believed to be involved in the pathologic processes behind Alzheimer's disease (AD). In this study, we aimed to examine the cerebrospinal fluid (CSF) levels of MMPs and tissue inhibitors of metalloproteinase-1 (TIMP-1) in individuals with AD dementia and cognitively healthy elderly individuals, and to investigate their relationship with established CSF biomarkers for Alzheimer's disease.

Methods

CSF was collected from 38 individuals with AD dementia and 34 cognitively healthy elderly individuals. The CSF was analyzed for MMP-1, MMP-3, MMP-9, TIMP-1, β-amyloid_1-42 (Aβ42), total tau protein (T-tau) and phosphorylated tau protein (P-tau). MMP/TIMP-1 ratios were calculated. APOE genotype was determined for the participants.

Results

AD patients had higher MMP-9/TIMP-1 ratios and lower TIMP-1 levels compared to cognitively healthy individuals. In AD patients, the MMP-9/TIMP-1 ratio correlated with CSF T-tau, a marker of neurodegeneration. Interestingly, the cognitively healthy individuals with risk markers for future AD, i.e. AD-supportive CSF biomarker levels of T-tau, P-tau and Aβ42 or the presence of the APOE ε4 allele, had higher CSF MMP-3 and MMP-9 levels and higher CSF MMP-3/TIMP-1 ratios compared to the healthy individuals without risk markers. The CSF levels of MMP-3 and -9 in the control group also correlated with the CSF T-tau and P-tau levels.

Conclusions

This study indicates that MMP-3 and MMP-9 might be involved in early pathogenesis of AD and that MMPs could be associated with neuronal degeneration and formation of neurofibrillary tangles even prior to development of overt cognitive dysfunction.

Matrix metalloproteinases-2 and -3 are reduced in cerebrospinal fluid with low beta-amyloid1-42 levels

Matrix metalloproteinases (MMPs), a family of extracellular soluble or membrane bound endopeptidases, are implicated in many physiological and pathophysiological functions-based on their capability to cleave all protein components of the extracellular matrix. Recent studies have implicated several forms of MMPs in chronic neurodegenerative diseases like Alzheimer's disease (AD), vascular dementia (VD), and Parkinson's disease (PD). The aim of the present study was to analyse eight MMPs (MMP-1, -2, -3, -7, -8, -9, -10, -13) in the human cerebrospinal fluid (CSF) and to correlate with the well established biomarkers beta-amyloid(1-42) (Abeta), total-tau and phospho-tau-181. Our data show a significant decrease of MMP-2 and MMP-3 levels in the CSF in samples with significantly reduced Abeta levels. It is concluded that MMP-2 and MMP-3 are directly linked to Abeta in the brain and a dysfunction may influence the processing of Abeta.

Cell-to-cell signaling at the neuromuscular junction: the dynamic role of the extracellular matrix

The extracellular matrix at the neuromuscular junction plays many roles. The matrix plays a structural role in that it maintains the spatial relationship between the muscle cell, Schwann cell, and presynaptic motor neuron. The matrix also plays a role in cell-to-cell signaling. The most studied member of this group is the heparan sulfate proteoglycan, agrin. Agrin is an integral member of the synaptic matrix, and it plays the pivotal role of instructing the muscle cell to aggregate acetylcholine receptors (AChRs) to the synapse. Agrin is released by the motor neuron, where it binds stably to the extracellular matrix. Agrin interacts with the muscle-specific tyrosine kinase (MuSK). Mice that lack agrin, or MuSK, fail to form neuromuscular junctions. Thus, the extracellular matrix is critical to both the structure and function of the neuromuscular junction. Remodeling of the extracellular matrix at the neuromuscular junction is needed to maintain stability, to allow growth, or to destabilize and remove synapses. Matrix metalloproteinases are key regulators of the extracellular matrix. In particular, matrix metalloproteinase 3 (MMP3) has been implicated in regulation of synaptic structure. MMP3 cleaves agrin. Antibodies to MMP3 recognize molecules concentrated at the synapses of frog neuromuscular junctions. Neuromuscular junctions in MMP3 null mutant mice have increased junctional folds, and AChR aggregates. Changes in synaptic activity will alter the activity of MMP3 at the synapse. Thus, the extracellular matrix is critical to the formation of the synapse, and synaptic activity controls the structure and function of the molecules in the extracellular matrix.

Neuronal 'On' and 'Off' signals control microglia

Recent findings indicate that neurons are not merely passive targets of microglia but rather control microglial activity. The variety of different signals that neurons use to control microglia can be divided into two categories: 'Off' signals constitutively keep microglia in their resting state and antagonize proinflammatory activity. 'On' signals are inducible and include purines, chemokines, glutamate. They instruct microglia activation under pathological conditions towards a beneficial or detrimental phenotype. Various neuronal signaling molecules thus actively control microglia function, thereby contribute to the inflammatory milieu of the central nervous system. Thus, neurons should be envisaged as key immune modulators in the brain.